fix: managed playback overlay lifecycle for launcher-owned sessions

- Remove --background from launcher-owned mpv starts; quit only non-tray/non-background managed sessions
- Defer autoplay-ready signal until overlay window content is loaded; retry after flush
- Retry socket availability before auto-starting overlay (up to 25 attempts, 200ms apart)
- Extract warm tokenization signal into autoplay-tokenization-warm-release with stale-media guard
- Queue second-instance commands until app ready runtime completes
- Guard globalShortcut cleanup with isAppReady check to avoid pre-ready crash
- Recognize "osx" as a macOS platform alias in Lua environment detection

src/main/runtime/mpv-main-event-main-deps.test.ts

@@ -92,7 +92,7 @@ test('mpv main event main deps map app state updates and delegate callbacks', as
   deps.maybeProbeAnilistDuration('media-key');
   deps.ensureAnilistMediaGuess('media-key');
   deps.syncImmersionMediaState();
-  deps.signalAutoplayReadyIfWarm('/tmp/video');
+  deps.signalAutoplayReadyIfWarm?.('/tmp/video');
   deps.updateCurrentMediaTitle('title');
   deps.resetAnilistMediaGuessState();
   deps.notifyImmersionTitleUpdate('title');