fix(topbar): the bar carries no action button

Creator ruling 2026-11-12: the action is not part of the output row, and it is not to be placed at all
until they say where. So Start Recording / Private Test Stream / Review & Go Live are out of the bar,
along with the divider that had been separating them.

What the middle of the bar is now: the world segment in Build, and the output line
(Output [YouTube] [Local MP4] One output at a time) in the Record / Go Live world. The view-model
commands (StartRecordingCommand, TestStreamCommand, GoLiveCommand) stay, unused by XAML, because they are
wherever the action lands next.

UiShellTests now asserts the bar contains none of the three action labels, so re-adding one by accident
fails the gate.

Scope justification: Assets/starting-background.jpg is outside this unit — the creator's replacement art,
still awaiting their visual check.

ytLive.Tests/UiShellTests.cs

@@ -49,10 +49,11 @@ public class UiShellTests
         Assert.Contains("IsChecked=\"{Binding OnAirPillOn}\"", topBar);
         Assert.Contains("IsChecked=\"{Binding RecordPillOn}\"", topBar);
 
-        // 2d. The action follows the armed output, and Test is an explicit ask again.
-        Assert.Contains("Content=\"Start Recording\"", topBar);
-        Assert.Contains("Content=\"Private Test Stream\"", topBar);
-        Assert.Contains("Content=\"Review & Go Live\"", topBar);
+        // 2d. The bar carries NO action button: the output line is the bar's whole middle
+        //     (creator ruling 2026-11-12 — the action is placed elsewhere, on instruction).
+        Assert.DoesNotContain("Content=\"Start Recording\"", topBar);
+        Assert.DoesNotContain("Content=\"Private Test Stream\"", topBar);
+        Assert.DoesNotContain("Content=\"Review & Go Live\"", topBar);
 
         // 3. Active scene = orange; live stays red.
         Assert.Contains("IsStaged}\" Value=\"True\">\n                                        <Setter Property=\"BorderBrush\" Value=\"{StaticResource Brush.Attention}\"/>", strip);