feat(audio dock): the shell — 168px, auto-collapsing, replacing the empty bottom bar

Unit 4 of the sound-bar refactor. `Controls/AudioDock` takes the bottom row that held the empty
`BottomBar` spacer (deleted): four bay containers (MIC / GAME / TRAX / LIP-SYNC) above a 36px
master strip, all token-styled.

Height comes from `Models/AudioDockLayout`, not from a setting: 168px normally, 36px below a 900px
window height. At the 1366×768 minimum a full dock leaves ~398px for the preview, so the collapse
is mandatory, not cosmetic. The dock listens to its window's SizeChanged and re-applies.

Nothing here pretends to be a meter yet — the bays and the master readouts fill in over the next
units, each with its own test.

Guard: AudioDockLayoutTests pins both sides of the threshold (768 collapsed, 1040 expanded), the
boundary itself, and the two heights as the design's numbers.

Controls/AudioDock.xaml

@@ -0,0 +1,58 @@
+<UserControl x:Class="ytLive.Controls.AudioDock"
+             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
+             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
+    <!-- The sound bars. Replaces the empty bottom-bar spacer; collapses to the telemetry strip
+         on short windows (AudioDockLayout decides the height, not this file). -->
+    <Border x:Name="DockRoot" Background="{StaticResource Brush.SurfaceContainer}"
+            BorderBrush="{StaticResource Brush.Outline}" BorderThickness="0,1,0,0">
+        <Grid>
+            <Grid.RowDefinitions>
+                <RowDefinition Height="*"/>
+                <RowDefinition Height="36"/>
+            </Grid.RowDefinitions>
+
+            <!-- Four bays: MIC | GAME | TRAX | SYNC. Filled in by the bay units. -->
+            <Grid x:Name="Bays" Grid.Row="0" Margin="8,6,8,0">
+                <Grid.ColumnDefinitions>
+                    <ColumnDefinition Width="*"/>
+                    <ColumnDefinition Width="*"/>
+                    <ColumnDefinition Width="*"/>
+                    <ColumnDefinition Width="*"/>
+                </Grid.ColumnDefinitions>
+
+                <Border Grid.Column="0" Background="{StaticResource Brush.SurfaceContainerLow}" CornerRadius="{StaticResource Radius.Sm}" Margin="0,0,4,0" Padding="10,6">
+                    <StackPanel>
+                        <TextBlock Text="MIC" FontSize="10" FontWeight="SemiBold" Foreground="{StaticResource Brush.OnSurfaceVariant}"/>
+                        <TextBlock x:Name="MicBayBody" Text="—" FontSize="11" Foreground="{StaticResource Brush.OnSurfaceDisabled}"/>
+                    </StackPanel>
+                </Border>
+                <Border Grid.Column="1" Background="{StaticResource Brush.SurfaceContainerLow}" CornerRadius="{StaticResource Radius.Sm}" Margin="4,0" Padding="10,6">
+                    <StackPanel>
+                        <TextBlock Text="GAME / PC" FontSize="10" FontWeight="SemiBold" Foreground="{StaticResource Brush.OnSurfaceVariant}"/>
+                        <TextBlock x:Name="GameBayBody" Text="—" FontSize="11" Foreground="{StaticResource Brush.OnSurfaceDisabled}"/>
+                    </StackPanel>
+                </Border>
+                <Border Grid.Column="2" Background="{StaticResource Brush.SurfaceContainerLow}" CornerRadius="{StaticResource Radius.Sm}" Margin="4,0" Padding="10,6">
+                    <StackPanel>
+                        <TextBlock Text="TRAX" FontSize="10" FontWeight="SemiBold" Foreground="{StaticResource Brush.OnSurfaceVariant}"/>
+                        <TextBlock x:Name="TraxBayBody" Text="—" FontSize="11" Foreground="{StaticResource Brush.OnSurfaceDisabled}"/>
+                    </StackPanel>
+                </Border>
+                <Border Grid.Column="3" Background="{StaticResource Brush.SurfaceContainerLow}" CornerRadius="{StaticResource Radius.Sm}" Margin="4,0,0,0" Padding="10,6">
+                    <StackPanel>
+                        <TextBlock Text="LIP-SYNC" FontSize="10" FontWeight="SemiBold" Foreground="{StaticResource Brush.OnSurfaceVariant}"/>
+                        <TextBlock x:Name="SyncBayBody" Text="—" FontSize="11" Foreground="{StaticResource Brush.OnSurfaceDisabled}"/>
+                    </StackPanel>
+                </Border>
+            </Grid>
+
+            <!-- Master strip: always visible, even collapsed — it is the telemetry line. -->
+            <Border x:Name="MasterStrip" Grid.Row="1" Background="{StaticResource Brush.SurfaceContainerLowest}" Padding="12,0">
+                <DockPanel VerticalAlignment="Center">
+                    <TextBlock DockPanel.Dock="Left" Text="MASTER" FontSize="10" FontWeight="SemiBold"
+                               Foreground="{StaticResource Brush.OnSurfaceVariant}" VerticalAlignment="Center"/>
+                </DockPanel>
+            </Border>
+        </Grid>
+    </Border>
+</UserControl>

Controls/AudioDock.xaml.cs

@@ -0,0 +1,55 @@
+using System.Windows;
+using System.Windows.Controls;
+using ytLive.Models;
+
+namespace ytLive.Controls;
+
+/// <summary>The sound bars (creator ruling 2026-10-30). This unit owns the SHELL: the piece of the
+/// window it occupies and the collapse behaviour. The bays and the master readouts fill in over
+/// the following units, so nothing here pretends to be a working meter.
+///
+/// <para>Collapse is driven by the window height, not a user setting: at 1366×768 a full dock
+/// squeezes the preview, and the creator should not have to manage that.</para></summary>
+public partial class AudioDock : UserControl
+{
+    private Window? _window;
+
+    public AudioDock()
+    {
+        InitializeComponent();
+        Loaded += OnLoaded;
+        Unloaded += OnUnloaded;
+    }
+
+    /// <summary>Is the dock showing only the telemetry strip?</summary>
+    internal bool IsCollapsed { get; private set; }
+
+    /// <summary>Test seam: the same code the window's SizeChanged runs, without a window.</summary>
+    internal void ApplyWindowHeight(double windowHeight)
+    {
+        var collapsed = AudioDockLayout.IsCollapsed(windowHeight);
+        IsCollapsed = collapsed;
+        Height = AudioDockLayout.HeightFor(windowHeight);
+        Bays.Visibility = collapsed ? Visibility.Collapsed : Visibility.Visible;
+    }
+
+    private void OnLoaded(object sender, RoutedEventArgs e)
+    {
+        _window = Window.GetWindow(this);
+        if (_window == null)
+        {
+            ApplyWindowHeight(AudioDockLayout.CollapseBelowHeight);   // no host: show the dock
+            return;
+        }
+        _window.SizeChanged += OnWindowSizeChanged;
+        ApplyWindowHeight(_window.ActualHeight > 0 ? _window.ActualHeight : _window.Height);
+    }
+
+    private void OnUnloaded(object sender, RoutedEventArgs e)
+    {
+        if (_window != null) _window.SizeChanged -= OnWindowSizeChanged;
+        _window = null;
+    }
+
+    private void OnWindowSizeChanged(object sender, SizeChangedEventArgs e) => ApplyWindowHeight(e.NewSize.Height);
+}

Controls/BottomBar.xaml

@@ -1,10 +0,0 @@
-<UserControl x:Class="ytLive.Controls.BottomBar"
-             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
-             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
-    <Border Background="#0f3460" Padding="16,4">
-        <Grid>
-            <!-- Intentionally empty. The hidden label keeps the bar's height unchanged. -->
-            <TextBlock Style="{StaticResource YtLabel}" Text=" " Visibility="Hidden"/>
-        </Grid>
-    </Border>
-</UserControl>

Controls/BottomBar.xaml.cs

@@ -1,11 +0,0 @@
-using System.Windows.Controls;
-
-namespace ytLive.Controls;
-
-public partial class BottomBar : UserControl
-{
-    public BottomBar()
-    {
-        InitializeComponent();
-    }
-}

MainWindow.xaml

@@ -148,7 +148,7 @@
         </Grid>
 
 
-        <controls:BottomBar Grid.Row="3"/>
+        <controls:AudioDock Grid.Row="3"/>
         <!-- ═══ OVERLAY: Settings / Bug / Feature / About ═══ -->
         <controls:OverlayHost Grid.RowSpan="3"/>
 

Models/AudioDockLayout.cs

@@ -0,0 +1,23 @@
+namespace ytLive.Models;
+
+/// <summary>How tall the audio dock should be for a given window height.
+///
+/// <para>Creator ruling (2026-10-30): the dock is 168px on a normal window and collapses to a 36px
+/// telemetry strip when the window is short, because at 1366×768 a full dock leaves ~398px for the
+/// preview and the composition starts letterboxing into a postage stamp.</para>
+///
+/// <para>Pure, so the switch is testable without a window.</para></summary>
+public static class AudioDockLayout
+{
+    /// <summary>Below this window height the dock collapses. The app's minimum is 768; the
+    /// default window is 1040, so a normal launch shows the full dock.</summary>
+    public const double CollapseBelowHeight = 900;
+
+    public const double ExpandedHeight = 168;
+    public const double CollapsedHeight = 36;
+
+    public static bool IsCollapsed(double windowHeight) => windowHeight < CollapseBelowHeight;
+
+    public static double HeightFor(double windowHeight)
+        => IsCollapsed(windowHeight) ? CollapsedHeight : ExpandedHeight;
+}

ytLive.Tests/AudioDockLayoutTests.cs

@@ -0,0 +1,32 @@
+using Xunit;
+using ytLive.Models;
+
+namespace ytLive.Tests;
+
+/// <summary>The dock's height is the whole reason it is allowed to take 168px: on a short window it
+/// must get out of the way instead of squeezing the preview. The threshold is the creator's
+/// minimum (768) and default (1040) — both sides are pinned here so a future "tidy" cannot leave a
+/// 768px window with a full dock.
+/// </summary>
+public class AudioDockLayoutTests
+{
+    [Fact]
+    public void The_dock_collapses_on_short_windows_and_expands_on_normal_ones()
+    {
+        // Minimum window: collapsed, so the preview keeps its room.
+        Assert.True(AudioDockLayout.IsCollapsed(768));
+        Assert.Equal(AudioDockLayout.CollapsedHeight, AudioDockLayout.HeightFor(768));
+
+        // Default window: the full dock.
+        Assert.False(AudioDockLayout.IsCollapsed(1040));
+        Assert.Equal(AudioDockLayout.ExpandedHeight, AudioDockLayout.HeightFor(1040));
+
+        // The boundary itself belongs to the expanded side (>= is the friendlier read).
+        Assert.False(AudioDockLayout.IsCollapsed(AudioDockLayout.CollapseBelowHeight));
+        Assert.True(AudioDockLayout.IsCollapsed(AudioDockLayout.CollapseBelowHeight - 1));
+
+        // The two heights are the design's numbers, not whatever looked fine.
+        Assert.Equal(168, AudioDockLayout.ExpandedHeight);
+        Assert.Equal(36, AudioDockLayout.CollapsedHeight);
+    }
+}