feat(ui): TASK 42 top bar redesign — one Record-or-Stream surface (2026-09-22)

The bar now renders ONE surface from the FIRST decision the creator makes —
Record or Stream — with each world being the whole bar. Creator directive:
"I wrote the fucking thing and I still can't figure-out how to do stuff",
"forget this one dog plan bullshit". OBS/streaming-tool reference for the
one-surface paradigm: https://obsproject.com (single mode toggle + context
actions) — cited per spin-guard habit; the go-live/test pattern follows
CEV (https://cev-desktop.aSean.xyz) precedent.

- Mode: single segmented REC|ON-AIR switch (SegmentToggle/SegmentLabel in
  Themes/Controls.xaml); radio-exclusive world selection, one tap to flip.
- Record world: switch + Start Recording, zero YouTube identity.
- Stream world: switch + Go Live + Test + account zone right (Sign In until
  connected, then avatar with Change Account/Logout context menu).
- Test is a child of Stream: procs only stream-armed AND signed-in.
- Running: one reality line "dot word elapsed" (REC/LIVE/TEST; green/red/
  gold) + End; worlds + switch retire.
- Gear moved up from bottom bar, ~3 wordmark letters past the brand, single
  click opens Settings/Bug/Feature/About menu (TASK 40 Unit B shipped early).
- Fix folded in: BeginTestStream now arms OnAirPillOn explicitly (unarmed
  pump booted with zero encoder outputs -> "At least one output is required"
  forced-stop cascade from TASK 41's pipeline).
- VM: world/reality props + RaiseTopBarModes() wired into StreamStatus,
  pill, IsRecording, IsTestStream, IsConnected setters.

Doc: ai.md top-bar model, ViewModels/index.md, Controls/index.md, TASKS.md,
HANDOFF.md, new TASKS/task-42-top-bar-redesign.md; task-40 note.

Tests: TopBarModeTests.cs (new Good Dog), PillRadioTests + TestStreamTests
gates updated. Build 0 warnings; full suite 314/315 — single abort is the
pre-existing env-dependent RealMouseDrag test (Path of Exile 2 running)

Themes/Controls.xaml

@@ -655,6 +655,42 @@
         </Setter>
     </Style>
 
+    <!-- Top-bar mode switch segments (top bar redesign): one two-position REC/ON-AIR
+         switch replaces the old pill pair — one binary decision, one world rendered.
+         The selected segment fills app-red and its label goes white. -->
+    <Style x:Key="SegmentToggle" TargetType="ToggleButton">
+        <Setter Property="Padding" Value="14,5"/>
+        <Setter Property="Cursor" Value="Hand"/>
+        <Setter Property="Template">
+            <Setter.Value>
+                <ControlTemplate TargetType="ToggleButton">
+                    <Border x:Name="Seg" Background="Transparent" CornerRadius="3"
+                            Padding="{TemplateBinding Padding}">
+                        <ContentPresenter HorizontalAlignment="Center" VerticalAlignment="Center"/>
+                    </Border>
+                    <ControlTemplate.Triggers>
+                        <Trigger Property="IsChecked" Value="True">
+                            <Setter TargetName="Seg" Property="Background" Value="#e94560"/>
+                        </Trigger>
+                    </ControlTemplate.Triggers>
+                </ControlTemplate>
+            </Setter.Value>
+        </Setter>
+    </Style>
+
+    <Style x:Key="SegmentLabel" TargetType="TextBlock">
+        <Setter Property="Foreground" Value="#a0a0b0"/>
+        <Setter Property="FontSize" Value="12"/>
+        <Setter Property="FontWeight" Value="Bold"/>
+        <Setter Property="VerticalAlignment" Value="Center"/>
+        <Style.Triggers>
+            <DataTrigger Binding="{Binding IsChecked, RelativeSource={RelativeSource AncestorType=ToggleButton}}"
+                         Value="True">
+                <Setter Property="Foreground" Value="White"/>
+            </DataTrigger>
+        </Style.Triggers>
+    </Style>
+
     <!-- Value-to-visibility converters, promoted from MainWindow.Window.Resources
          so extracted UserControls can resolve them (AGENTS: controls must not
          reach into a window's own resources; they share the app-level theme). -->