From 90f5ad50dd693543fdbdd147bb2c2b8a988e52dd Mon Sep 17 00:00:00 2001
From: gramps <gramps@llamachile.shop>
Date: Sun, 30 Aug 2026 09:13:47 -0700
Subject: [PATCH] =?UTF-8?q?refactor:=20extract=20TopBar=20out=20of=20MainW?=
 =?UTF-8?q?indow.xaml=20=E2=80=94=20Phase=202,=20Commit=2014?=
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TopBar.xaml(.cs) takes the Row 0 top controls: logo/About button, REC/ON-AIR
pills + status signs, avatar, Sign In/Start/End buttons. The avatar fetch
(AvatarHttp/_loadedAvatarUrl/LoadAvatarImage/ShowAvatarFallback) moved into the
control with async semantics preserved; the window grabs the control via
FindName in its ctor and calls _topBar.RefreshAvatar() when IsConnected or
AccountAvatarUrl changes (previously OnViewModelPropertyChanged -> LoadAvatarImage).
AccountLight is pure binding (never touched by code-behind) so it moved with the XAML.

Zero behavior change; build 0 warnings; 246 pass, only the 2 known failures.
Also dropped the now-unused System.IO using from MainWindow.xaml.cs.
Docs: ViewModels/index.md Phase 2 tracker updated in the same commit.
---
 Controls/TopBar.xaml    | 118 ++++++++++++++++++++++++++++++++++++++++
 Controls/TopBar.xaml.cs |  72 ++++++++++++++++++++++++
 MainWindow.xaml         | 114 +-------------------------------------
 MainWindow.xaml.cs      |  55 ++-----------------
 ViewModels/index.md     |   3 +-
 5 files changed, 197 insertions(+), 165 deletions(-)
 create mode 100644 Controls/TopBar.xaml
 create mode 100644 Controls/TopBar.xaml.cs

diff --git a/Controls/TopBar.xaml b/Controls/TopBar.xaml
new file mode 100644
index 0000000..d53a6f2
--- /dev/null
+++ b/Controls/TopBar.xaml
@@ -0,0 +1,118 @@
+<UserControl x:Class="ytLive.Controls.TopBar"
+             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
+             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+             x:Name="TopBarRoot">
+    <!-- LOGO / BRAND — clicking opens the in-app About overlay -->
+    <Grid>
+        <Grid.ColumnDefinitions>
+            <ColumnDefinition Width="Auto"/>
+            <ColumnDefinition Width="*"/>
+            <ColumnDefinition Width="Auto"/>
+        </Grid.ColumnDefinitions>
+
+        <!-- Logo / Brand — clicking opens the in-app About overlay -->
+        <Button Grid.Column="0" Background="Transparent" BorderThickness="0" Cursor="Hand"
+                VerticalAlignment="Center" Margin="0,0,24,0" ToolTip="About LlamaCasty"
+                Command="{Binding OpenAboutCommand}">
+            <Button.Template>
+                <ControlTemplate TargetType="Button">
+                    <ContentPresenter/>
+                </ControlTemplate>
+            </Button.Template>
+            <TextBlock FontSize="22" FontWeight="Bold">
+                <Run Text="LlamaCas" Foreground="#e0e0e0"/><Run Text="ty" Foreground="#e94560"/>
+            </TextBlock>
+        </Button>
+
+        <!-- REC / ON-AIR pills (intent) + status signs (reality) -->
+        <StackPanel Grid.Column="1" Orientation="Horizontal"
+                    HorizontalAlignment="Center" VerticalAlignment="Center">
+            <!-- REC pill: local recording needs no sign-in -->
+            <TextBlock Text="REC" Foreground="#e94560" FontWeight="Bold" FontSize="12"
+                       VerticalAlignment="Center" Margin="0,0,6,0"/>
+            <ToggleButton Style="{StaticResource PillToggle}" VerticalAlignment="Center"
+                          IsChecked="{Binding RecordPillOn}"/>
+            <!-- ON-AIR pill: greyed out until signed in -->
+            <TextBlock Text="ON-AIR" Foreground="#e94560" FontWeight="Bold" FontSize="12"
+                       VerticalAlignment="Center" Margin="16,0,6,0"/>
+            <ToggleButton Style="{StaticResource PillToggle}" VerticalAlignment="Center"
+                          IsChecked="{Binding OnAirPillOn}"
+                          IsEnabled="{Binding CanToggleOnAir}"
+                          ToolTip="{Binding AccountStatusLightToolTip}"/>
+            <!-- Status signs: REC dot + ON-AIR dot -->
+            <Ellipse Width="12" Height="12" VerticalAlignment="Center" Margin="16,0,0,0"
+                     Fill="{Binding RecDotBrush}" Opacity="{Binding RecDotOpacity}"/>
+            <TextBlock Text="REC" Style="{StaticResource StatusSignText}"/>
+            <!-- ON-AIR sign: gray offline, red public, green private -->
+            <Ellipse Width="12" Height="12" VerticalAlignment="Center" Margin="16,0,0,0"
+                     Fill="{Binding OnAirBrush}"/>
+            <TextBlock Text="ON-AIR" Style="{StaticResource StatusSignText}"/>
+            <Border Background="#8f1f1f" CornerRadius="3" Padding="6,1" Margin="8,0,0,0"
+                    VerticalAlignment="Center"
+                    Visibility="{Binding IsLivePrivate, Converter={StaticResource BoolToVis}}">
+                <TextBlock Text="PRIVATE" FontSize="11" FontWeight="Bold" Foreground="White"/>
+            </Border>
+            <TextBlock Text="{Binding LiveElapsedText}" Foreground="White" FontSize="14"
+                       FontFamily="Consolas" VerticalAlignment="Center" Margin="14,0,0,0"
+                       Visibility="{Binding IsLive, Converter={StaticResource BoolToVis}}"/>
+        </StackPanel>
+
+        <!-- Three-state top bar: logged-out / idle / live -->
+        <StackPanel Grid.Column="2" Orientation="Horizontal" VerticalAlignment="Center">
+            <!-- Status light -->
+            <Ellipse Width="8" Height="8" Margin="0,0,8,0" VerticalAlignment="Center"
+                     ToolTip="{Binding AccountStatusLightToolTip}">
+                <Ellipse.Style>
+                    <Style TargetType="Ellipse">
+                        <Setter Property="Fill" Value="#ef4444"/>
+                        <Style.Triggers>
+                            <DataTrigger Binding="{Binding IsConnected}" Value="True">
+                                <Setter Property="Fill" Value="#22c55e"/>
+                            </DataTrigger>
+                            <DataTrigger Binding="{Binding IsLive}" Value="True">
+                                <Setter Property="Fill" Value="#e94560"/>
+                            </DataTrigger>
+                        </Style.Triggers>
+                    </Style>
+                </Ellipse.Style>
+            </Ellipse>
+            <!-- Avatar (connected only); shows the channel initial when
+                 the profile image is missing or fails to download -->
+            <Border Width="26" Height="26" CornerRadius="13" Background="#16213e" ClipToBounds="True"
+                    Margin="0,0,8,0" VerticalAlignment="Center"
+                    ToolTip="{Binding AccountDisplayName}"
+                    Visibility="{Binding IsConnected, Converter={StaticResource BoolToVis}}">
+                <Grid>
+                    <Image x:Name="AvatarImage" Stretch="UniformToFill"/>
+                    <TextBlock x:Name="AvatarInitial" Foreground="#e0e0e0" FontSize="13"
+                               FontWeight="Bold" HorizontalAlignment="Center" VerticalAlignment="Center"
+                               Visibility="Collapsed"/>
+                </Grid>
+            </Border>
+            <!-- Sign In button (disconnected + offline) -->
+            <Button Content="Sign In" Style="{StaticResource YtButton}"
+                    Margin="0,0,12,0"
+                    Command="{Binding StartStreamCommand}"
+                    Visibility="{Binding ShowLogInButton, Converter={StaticResource BoolToVis}}"/>
+            <!-- Primary Start button (offline): dynamic label from the pills -->
+            <Button Content="Start" Style="{StaticResource YtButton}"
+                    Command="{Binding StartStreamCommand}"
+                    Visibility="{Binding ShowPrimaryStartButton, Converter={StaticResource BoolToVis}}">
+                <Button.ContextMenu>
+                    <ContextMenu>
+                        <MenuItem Header="Choose Record Folder" Command="{Binding ChooseRecordFolderCommand}"/>
+                        <Separator/>
+                        <MenuItem Header="Change Account" Command="{Binding ChangeAccountCommand}"/>
+                        <Separator/>
+                        <MenuItem Header="Logout" Command="{Binding LogoutCommand}"/>
+                    </ContextMenu>
+                </Button.ContextMenu>
+            </Button>
+            <!-- End button (live OR recording) — the only button whose
+                 label changes; "Stop Recording" while recording -->
+            <Button Content="{Binding EndButtonText}" Style="{StaticResource YtButton}"
+                    Background="#333" Command="{Binding EndStreamCommand}"
+                    Visibility="{Binding ShowEndStreamButton, Converter={StaticResource BoolToVis}}"/>
+        </StackPanel>
+    </Grid>
+</UserControl>
\ No newline at end of file
diff --git a/Controls/TopBar.xaml.cs b/Controls/TopBar.xaml.cs
new file mode 100644
index 0000000..2e1ef25
--- /dev/null
+++ b/Controls/TopBar.xaml.cs
@@ -0,0 +1,72 @@
+using System;
+using System.IO;
+using System.Net.Http;
+using System.Windows.Controls;
+using System.Windows.Media.Imaging;
+using ytLive.Helpers;
+using ytLive.ViewModels;
+
+namespace ytLive.Controls;
+
+public partial class TopBar : UserControl
+{
+    private static readonly HttpClient AvatarHttp = new() { Timeout = TimeSpan.FromSeconds(15) };
+    private string? _loadedAvatarUrl;
+
+    public TopBar()
+    {
+        InitializeComponent();
+        AvatarImage.Source = null;
+        AvatarInitial.Visibility = System.Windows.Visibility.Collapsed;
+    }
+
+    public void RefreshAvatar()
+    {
+        _ = LoadAvatarImageAsync();
+    }
+
+    private async System.Threading.Tasks.Task LoadAvatarImageAsync()
+    {
+        var vm = DataContext as MainViewModel;
+        var url = vm?.AccountAvatarUrl;
+        if (vm is not { IsConnected: true })
+        {
+            ShowAvatarFallback(null);
+            return;
+        }
+        if (string.IsNullOrWhiteSpace(url))
+        {
+            AppLog.Write("Avatar: connected but no profile image URL on the session");
+            ShowAvatarFallback(null);
+            return;
+        }
+        if (url == _loadedAvatarUrl && AvatarImage.Source != null) return;
+        try
+        {
+            var bytes = await AvatarHttp.GetByteArrayAsync(url);
+            using var ms = new MemoryStream(bytes);
+            var bitmap = new BitmapImage();
+            bitmap.BeginInit();
+            bitmap.CacheOption = BitmapCacheOption.OnLoad;
+            bitmap.StreamSource = ms;
+            bitmap.EndInit();
+            bitmap.Freeze();
+            _loadedAvatarUrl = url;
+            AvatarImage.Source = bitmap;
+            AvatarInitial.Visibility = System.Windows.Visibility.Collapsed;
+        }
+        catch (Exception ex)
+        {
+            AppLog.Write($"Avatar load failed ({url}): {ex.Message}");
+            ShowAvatarFallback(vm?.AccountDisplayName);
+        }
+    }
+
+    private void ShowAvatarFallback(string? name)
+    {
+        _loadedAvatarUrl = null;
+        AvatarImage.Source = null;
+        AvatarInitial.Text = string.IsNullOrWhiteSpace(name) ? "?" : name.Substring(0, 1).ToUpperInvariant();
+        AvatarInitial.Visibility = System.Windows.Visibility.Visible;
+    }
+}
\ No newline at end of file
diff --git a/MainWindow.xaml b/MainWindow.xaml
index 4999fbe..8e8f28a 100644
--- a/MainWindow.xaml
+++ b/MainWindow.xaml
@@ -76,119 +76,7 @@
 
         <!-- ═══ TOP BAR: Stream Controls ═══ -->
         <Border Grid.Row="0" Background="{Binding TopBarBackground}" Padding="16,10">
-            <Grid>
-                <Grid.ColumnDefinitions>
-                    <ColumnDefinition Width="Auto"/>
-                    <ColumnDefinition Width="*"/>
-                    <ColumnDefinition Width="Auto"/>
-                </Grid.ColumnDefinitions>
-
-                <!-- Logo / Brand — clicking opens the in-app About overlay -->
-                <Button Grid.Column="0" Background="Transparent" BorderThickness="0" Cursor="Hand"
-                        VerticalAlignment="Center" Margin="0,0,24,0" ToolTip="About LlamaCasty"
-                        Command="{Binding OpenAboutCommand}">
-                    <Button.Template>
-                        <ControlTemplate TargetType="Button">
-                            <ContentPresenter/>
-                        </ControlTemplate>
-                    </Button.Template>
-                    <TextBlock FontSize="22" FontWeight="Bold">
-                        <Run Text="LlamaCas" Foreground="#e0e0e0"/><Run Text="ty" Foreground="#e94560"/>
-                    </TextBlock>
-                </Button>
-
-                <!-- REC / ON-AIR pills (intent) + status signs (reality) -->
-                <StackPanel Grid.Column="1" Orientation="Horizontal"
-                            HorizontalAlignment="Center" VerticalAlignment="Center">
-                    <!-- REC pill: local recording needs no sign-in -->
-                    <TextBlock Text="REC" Foreground="#e94560" FontWeight="Bold" FontSize="12"
-                               VerticalAlignment="Center" Margin="0,0,6,0"/>
-                    <ToggleButton Style="{StaticResource PillToggle}" VerticalAlignment="Center"
-                                  IsChecked="{Binding RecordPillOn}"/>
-                    <!-- ON-AIR pill: greyed out until signed in -->
-                    <TextBlock Text="ON-AIR" Foreground="#e94560" FontWeight="Bold" FontSize="12"
-                               VerticalAlignment="Center" Margin="16,0,6,0"/>
-                    <ToggleButton Style="{StaticResource PillToggle}" VerticalAlignment="Center"
-                                  IsChecked="{Binding OnAirPillOn}"
-                                  IsEnabled="{Binding CanToggleOnAir}"
-                                  ToolTip="{Binding AccountStatusLightToolTip}"/>
-                    <!-- Status signs: REC dot + ON-AIR dot -->
-                    <Ellipse Width="12" Height="12" VerticalAlignment="Center" Margin="16,0,0,0"
-                             Fill="{Binding RecDotBrush}" Opacity="{Binding RecDotOpacity}"/>
-                    <TextBlock Text="REC" Style="{StaticResource StatusSignText}"/>
-                    <!-- ON-AIR sign: gray offline, red public, green private -->
-                    <Ellipse Width="12" Height="12" VerticalAlignment="Center" Margin="16,0,0,0"
-                             Fill="{Binding OnAirBrush}"/>
-                    <TextBlock Text="ON-AIR" Style="{StaticResource StatusSignText}"/>
-                    <Border Background="#8f1f1f" CornerRadius="3" Padding="6,1" Margin="8,0,0,0"
-                            VerticalAlignment="Center"
-                            Visibility="{Binding IsLivePrivate, Converter={StaticResource BoolToVis}}">
-                        <TextBlock Text="PRIVATE" FontSize="11" FontWeight="Bold" Foreground="White"/>
-                    </Border>
-                    <TextBlock Text="{Binding LiveElapsedText}" Foreground="White" FontSize="14"
-                               FontFamily="Consolas" VerticalAlignment="Center" Margin="14,0,0,0"
-                               Visibility="{Binding IsLive, Converter={StaticResource BoolToVis}}"/>
-                </StackPanel>
-
-                <!-- Three-state top bar: logged-out / idle / live -->
-                <StackPanel Grid.Column="2" Orientation="Horizontal" VerticalAlignment="Center">
-                    <!-- Status light -->
-                    <Ellipse Width="8" Height="8" Margin="0,0,8,0" VerticalAlignment="Center"
-                             ToolTip="{Binding AccountStatusLightToolTip}"
-                             x:Name="AccountLight">
-                        <Ellipse.Style>
-                            <Style TargetType="Ellipse">
-                                <Setter Property="Fill" Value="#ef4444"/>
-                                <Style.Triggers>
-                                    <DataTrigger Binding="{Binding IsConnected}" Value="True">
-                                        <Setter Property="Fill" Value="#22c55e"/>
-                                    </DataTrigger>
-                                    <DataTrigger Binding="{Binding IsLive}" Value="True">
-                                        <Setter Property="Fill" Value="#e94560"/>
-                                    </DataTrigger>
-                                </Style.Triggers>
-                            </Style>
-                        </Ellipse.Style>
-                    </Ellipse>
-                    <!-- Avatar (connected only); shows the channel initial when
-                         the profile image is missing or fails to download -->
-                    <Border Width="26" Height="26" CornerRadius="13" Background="#16213e" ClipToBounds="True"
-                            Margin="0,0,8,0" VerticalAlignment="Center"
-                            ToolTip="{Binding AccountDisplayName}"
-                            Visibility="{Binding IsConnected, Converter={StaticResource BoolToVis}}">
-                        <Grid>
-                            <Image x:Name="AvatarImage" Stretch="UniformToFill"/>
-                            <TextBlock x:Name="AvatarInitial" Foreground="#e0e0e0" FontSize="13"
-                                       FontWeight="Bold" HorizontalAlignment="Center" VerticalAlignment="Center"
-                                       Visibility="Collapsed"/>
-                        </Grid>
-                    </Border>
-                    <!-- Sign In button (disconnected + offline) -->
-                    <Button Content="Sign In" Style="{StaticResource YtButton}"
-                            Margin="0,0,12,0"
-                            Command="{Binding StartStreamCommand}"
-                            Visibility="{Binding ShowLogInButton, Converter={StaticResource BoolToVis}}"/>
-                    <!-- Primary Start button (offline): dynamic label from the pills -->
-                    <Button Content="Start" Style="{StaticResource YtButton}"
-                            Command="{Binding StartStreamCommand}"
-                            Visibility="{Binding ShowPrimaryStartButton, Converter={StaticResource BoolToVis}}">
-                        <Button.ContextMenu>
-                            <ContextMenu>
-                                <MenuItem Header="Choose Record Folder" Command="{Binding ChooseRecordFolderCommand}"/>
-                                <Separator/>
-                                <MenuItem Header="Change Account" Command="{Binding ChangeAccountCommand}"/>
-                                <Separator/>
-                                <MenuItem Header="Logout" Command="{Binding LogoutCommand}"/>
-                            </ContextMenu>
-                        </Button.ContextMenu>
-                    </Button>
-                    <!-- End button (live OR recording) — the only button whose
-                         label changes; "Stop Recording" while recording -->
-                    <Button Content="{Binding EndButtonText}" Style="{StaticResource YtButton}"
-                            Background="#333" Command="{Binding EndStreamCommand}"
-                            Visibility="{Binding ShowEndStreamButton, Converter={StaticResource BoolToVis}}"/>
-                </StackPanel>
-            </Grid>
+            <controls:TopBar x:Name="TopBar"/>
         </Border>
 
         <!-- ═══ MIDDLE: Main Content ═══ -->
diff --git a/MainWindow.xaml.cs b/MainWindow.xaml.cs
index afe5cc7..b111425 100644
--- a/MainWindow.xaml.cs
+++ b/MainWindow.xaml.cs
@@ -1,7 +1,6 @@
 using System;
 using System.Collections;
 using System.ComponentModel;
-using System.IO;
 using System.Net.Http;
 using System.Windows;
 using System.Windows.Controls;
@@ -22,6 +21,7 @@ public partial class MainWindow : Window
 {
     private readonly MainViewModel _viewModel;
     private readonly Dictionary<string, Storyboard> _activeBorderAnimations = new();
+    private Controls.TopBar _topBar = null!;
 
     public MainWindow()
     {
@@ -34,8 +34,8 @@ public partial class MainWindow : Window
         _viewModel.ChatMessages.CollectionChanged += OnChatMessagesChanged;
         UpdateTaskbarOverlay();
         UpdateSelectionOverlay();
-        AvatarImage.Source = null;
-        AvatarInitial.Visibility = Visibility.Collapsed;
+        _topBar = (Controls.TopBar)FindName("TopBar")!;
+        _topBar.RefreshAvatar();
         RestoreWindowGeometry();
         AppLog.Write("MainWindow ctor: end");
     }
@@ -116,7 +116,7 @@ public partial class MainWindow : Window
             UpdateSelectionOverlay();
         else if (e.PropertyName == nameof(MainViewModel.AccountAvatarUrl)
               || e.PropertyName == nameof(MainViewModel.IsConnected))
-            LoadAvatarImage();
+            _topBar.RefreshAvatar();
     }
 
     private void MainWindow_Closing(object? sender, CancelEventArgs e)
@@ -141,53 +141,6 @@ public partial class MainWindow : Window
             : null;
     }
 
-    private static readonly HttpClient AvatarHttp = new() { Timeout = TimeSpan.FromSeconds(15) };
-    private string? _loadedAvatarUrl;
-
-    private async void LoadAvatarImage()
-    {
-        var url = _viewModel.AccountAvatarUrl;
-        if (!_viewModel.IsConnected)
-        {
-            ShowAvatarFallback(null);
-            return;
-        }
-        if (string.IsNullOrWhiteSpace(url))
-        {
-            AppLog.Write("Avatar: connected but no profile image URL on the session");
-            ShowAvatarFallback(null);
-            return;
-        }
-        if (url == _loadedAvatarUrl && AvatarImage.Source != null) return;
-        try
-        {
-            var bytes = await AvatarHttp.GetByteArrayAsync(url);
-            using var ms = new MemoryStream(bytes);
-            var bitmap = new BitmapImage();
-            bitmap.BeginInit();
-            bitmap.CacheOption = BitmapCacheOption.OnLoad;
-            bitmap.StreamSource = ms;
-            bitmap.EndInit();
-            bitmap.Freeze();
-            _loadedAvatarUrl = url;
-            AvatarImage.Source = bitmap;
-            AvatarInitial.Visibility = Visibility.Collapsed;
-        }
-        catch (Exception ex)
-        {
-            AppLog.Write($"Avatar load failed ({url}): {ex.Message}");
-            ShowAvatarFallback(_viewModel.AccountDisplayName);
-        }
-    }
-
-    private void ShowAvatarFallback(string? name)
-    {
-        _loadedAvatarUrl = null;
-        AvatarImage.Source = null;
-        AvatarInitial.Text = string.IsNullOrWhiteSpace(name) ? "?" : name.Substring(0, 1).ToUpperInvariant();
-        AvatarInitial.Visibility = Visibility.Visible;
-    }
-
     private void SourceNameBox_IsVisibleChanged(object sender, DependencyPropertyChangedEventArgs e)
     {
         if (sender is TextBox { IsVisible: true } box)
diff --git a/ViewModels/index.md b/ViewModels/index.md
index 006ccc1..e185ded 100644
--- a/ViewModels/index.md
+++ b/ViewModels/index.md
@@ -55,7 +55,8 @@ Progress (Commit N/12 · tag):
 
 **Phase 2 — `MainWindow.xaml` split into UserControls** (new `Controls/` folder, namespace `ytLive.Controls`):
 - [x] **Commit 12 · `refactor-commit-12`** — **BottomBar** → `Controls/BottomBar.xaml(.cs)` (gear menu + stream stats + quality dropdown; `GearButton_Click` moved to the control's code-behind).
-- [x] **Commit 13 · `refactor-commit-13`** — **HealthBanner** → `Controls/HealthBanner.xaml` (Row 1). Also promoted the 7 value↔visibility converters out of `MainWindow.Window.Resources` into `Themes/Controls.xaml` so extracted controls can resolve them (app-level, not window-level). Pending: TopBar, left scene/chat panel, preview pane, overlay host.
+- [x] **Commit 13 · `refactor-commit-13`** — **HealthBanner** → `Controls/HealthBanner.xaml` (Row 1). Also promoted the 7 value↔visibility converters out of `MainWindow.Window.Resources` into `Themes/Controls.xaml` so extracted controls can resolve them (app-level, not window-level).
+- [x] **Commit 14 · `refactor-commit-14`** — **TopBar** → `Controls/TopBar.xaml(.cs)` (Row 0: logo, REC/ON-AIR pills + signs, avatar, Sign In/Start/End buttons). Avatar fetch moved (async-preserved) into the control; window exposes `_topBar.RefreshAvatar()` invoked on `IsConnected`/`AccountAvatarUrl` changes. Pending: left scene/chat panel, preview pane, overlay host.
 
 The partial `.cs` files land next to `MainViewModel.cs` in this folder as the split
 proceeds; each partial carries its own `using`s and re-declares nothing from core.
\ No newline at end of file