Layers panel and scene strip: scene layers header with icons, per-type layer icons, PROGRAM badge and selected/live orange borders, scene name and hotkey overlays, Starting as default scene

- LeftPanel: SCENE LAYERS header with layer count; per-type blue icons; properties header gear; layers list min/max height; properties placeholder; list and properties indent
- SceneThumbnailStrip: names/hotkeys over the tile; PROGRAM badge with blinking red dot on the selected tile; orange border on selected and live tiles; fixed the element border override that hid the style border; reflag tiles on load
- LiveScene is now set on go-live, record start, and live transitions (it was never assigned, so IsLive never fired)
- Startup stages the scene named Starting
- DESIGN.md: color roles (red = YouTube/on-air/record, orange #ff8c3a = attention, amber = game audio/Super Chat)
- Staged live tile uses background art instead of the green LIVE placeholder

Not pushed.

ViewModels/MainViewModel.Streaming.Operations.cs

@@ -65,6 +65,7 @@ public partial class MainViewModel : ViewModelBase
         ResetHealth(StreamStatus.Offline);
         _audioMixer.StartLive(EncoderOptions.DefaultAudioPipeName);
         IsRecording = true;
+        LiveScene = StagedScene;
         await _framePump.StartAsync();
     }
 
@@ -222,6 +223,7 @@ public partial class MainViewModel : ViewModelBase
         // only once frames flow. The liveChatId (snippet.liveChatId) does not exist
         // before that (2026-09-25 diagnosis), so chat resolution runs AFTER the pump
         // starts. Chat is non-fatal — if it fails, the stream continues without chat.
+        LiveScene = StagedScene;
         await _framePump.StartAsync(); // never throws; failures log + surface via Failed
 
         string? liveChatId = null;
@@ -324,6 +326,7 @@ public partial class MainViewModel : ViewModelBase
 
         StreamStatus = StreamStatus.Offline;
         IsRecording = false;
+        LiveScene = null;
         // TASK 41: a stopped test broadcast forgets its drawer session (idempotent)
         // and drops the TEST face — a test never outlives its run.
         TestSession.EndTestSilently();