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/shared/ipc/contracts.ts

@@ -29,6 +29,8 @@ export const ipcChannels = {
     setCurrentScene: 'project.setCurrentScene',
     setCurrentGraphNode: 'project.setCurrentGraphNode',
     importMedia: 'project.importMedia',
+    importCampaignAudio: 'project.importCampaignAudio',
+    updateCampaignAudios: 'project.updateCampaignAudios',
     importScenePreview: 'project.importScenePreview',
     clearScenePreview: 'project.clearScenePreview',
     assetFileUrl: 'project.assetFileUrl',
@@ -120,6 +122,14 @@ export type IpcInvokeMap = {
     req: { sceneId: SceneId };
     res: { project: Project; imported: MediaAsset[] };
   };
+  [ipcChannels.project.importCampaignAudio]: {
+    req: Record<string, never>;
+    res: { canceled: boolean; project: Project; imported: MediaAsset[] };
+  };
+  [ipcChannels.project.updateCampaignAudios]: {
+    req: { audios: Project['campaignAudios'] };
+    res: { project: Project };
+  };
   [ipcChannels.project.importScenePreview]: {
     req: { sceneId: SceneId };
     res: { project: Project };