fix(jellyfin): show overlay, inject plugin, and fix stats title on playb

- Show visible overlay automatically during Jellyfin playback so subtitleStyle applies
- Inject bundled mpv plugin on auto-launch so keybindings work without overlay focus
- Group Jellyfin playback stats under item metadata (jellyfin://host/item/id) instead of stream URLs so episodes merge with matching local titles
- Mark ffsubsync unavailable in subsync modal for remote media paths
- Drain queued second-instance commands even when onReady throws

src/main/runtime/app-lifecycle-actions.ts

@@ -29,6 +29,7 @@ export function createOnWillQuitCleanupHandler(deps: {
   clearYomitanSettingsWindow: () => void;
   stopJellyfinRemoteSession: () => void;
   cleanupYoutubeSubtitleTempDirs: () => void;
+  cleanupJellyfinSubtitleCache: () => void;
   stopDiscordPresenceService: () => void;
 }) {
   return (): void => {
@@ -62,6 +63,7 @@ export function createOnWillQuitCleanupHandler(deps: {
     deps.clearYomitanSettingsWindow();
     deps.stopJellyfinRemoteSession();
     deps.cleanupYoutubeSubtitleTempDirs();
+    deps.cleanupJellyfinSubtitleCache();
     deps.stopDiscordPresenceService();
   };
 }