feat(scoreboard): it ticks — the marquee is the design, not an option

Creator, plainly: "the entire point of a ticker is to tick… so, tick." The static strip was my
reading of an earlier exchange; it is gone.

How it ticks without becoming the compositor's most expensive layer:
- `ScoreboardRenderer.RenderRun` rasterises the run ONCE per value change at its natural width plus
  a gap.
- `ScoreboardPresenter` crops a 1920-wide window at a moving offset each tick — a row-wise byte
  copy, no text layout, no re-raster.
- `TickScoreboard` runs on the existing 30 Hz meter clock and only while the strip is shown, so a
  hidden or disabled scoreboard costs nothing.

The dev simulation uses the same path, so what is previewed is what ships.

Test updated to the real contract: no tick → identical pixels; a tick → different pixels; a value
change → re-rasterised run. (The old test asserted frame-instance identity, which a cropped window
can never satisfy.)

ViewModels/MainViewModel.Audio.cs

@@ -31,6 +31,7 @@ public partial class MainViewModel
         RaiseMasterReadouts();
         UpdateDuckState();
         CheckTraxSilence();
+        TickScoreboard();
     }
 
     /// <summary>One honest diagnostic: "playing" with a flat player meter means the samples never

ViewModels/MainViewModel.Scoreboard.cs

@@ -89,8 +89,14 @@ public partial class MainViewModel
         set
         {
             if (!SetProperty(ref _scoreboardSimulate, value)) return;
-            if (value) ScoreboardSample.Inject(_scoreboard);
-            else _scoreboard.StartSession();          // empty session: "nothing yet"
+            if (value)
+            {
+                ScoreboardSample.Inject(_scoreboard);
+            }
+            else
+            {
+                _scoreboard.StartSession();          // empty session: "nothing yet"
+            }
             RefreshScoreboardPreviews();
             OnPropertyChanged(nameof(ScoreboardFrame));
         }
@@ -98,7 +104,8 @@ public partial class MainViewModel
 
     /// <summary>What the cadence policy asks: the master switch AND at least one scene showing it.</summary>
     internal bool ScoreboardPollsEnabled =>
-        _scoreboardEnabled && Scenes.Any(scene =>
+        !_scoreboardSimulate                        // dev data is made up: never poll for it
+        && _scoreboardEnabled && Scenes.Any(scene =>
             scene.Elements.OfType<Source>().Any(s => s.IsScoreboard && s.IsVisible && s.IsEnabled));
 
     internal ScoreboardTiles ScoreboardTilesState => _scoreboardTiles;
@@ -215,6 +222,16 @@ public partial class MainViewModel
         OnPropertyChanged(nameof(ScoreboardStyleState));
     }
 
+    /// <summary>One tick of the marquee: advance the window and republish. Runs only while the strip
+    /// is actually shown, so an idle/hidden scoreboard costs nothing.</summary>
+    private void TickScoreboard()
+    {
+        if (_scoreboardPresenter is null) return;
+        if (!_scoreboardEnabled && !_scoreboardSimulate) return;
+        _scoreboardPresenter.Advance(0.033);
+        RefreshScoreboardPreviews();
+    }
+
     /// <summary>Publishes the strip to every scoreboard layer's preview element. The pump thread
     /// must never touch a WriteableBitmap, so this runs on the UI thread only.</summary>
     private void RefreshScoreboardPreviews()