fix: game audio persistence and editor perf

- Keep game/campaign audio assets referenced (no prune)
- Flush pending project save on quit/switch/export to avoid losing campaignAudios
- Control: prevent game music restarts on scene changes; allow always-on controls; handle autoplay-after-scene-audio
- Editor: reduce ReactFlow churn with stable scene card map; lazy/async image decode
- Add contract/unit tests and update test script

Made-with: Cursor

app/main/project/assetPrune.ts

@@ -12,6 +12,7 @@ export function collectReferencedAssetIds(p: Project): Set<AssetId> {
     for (const vid of sc.media.videos) refs.add(vid);
     for (const au of sc.media.audios) refs.add(au.assetId);
   }
+  for (const au of p.campaignAudios) refs.add(au.assetId);
   return refs;
 }