refactor: make subsync manual-only, default opt-in features off, preserv

- Remove subsync.defaultMode; subsync always opens manual picker
- Default jellyfinRemoteSession warmup and nameMatchEnabled to false
- Stop rewriting config file during legacy migration (resolve in-memory only)
- Fix macOS quit on window-close for --setup launch mode

src/config/definitions/defaults-core.ts

@@ -105,7 +105,6 @@ export const CORE_DEFAULT_CONFIG: Pick<
     primarySubLanguages: ['ja', 'jpn'],
   },
   subsync: {
-    defaultMode: 'auto',
     alass_path: '',
     ffsubsync_path: '',
     ffmpeg_path: '',
@@ -116,7 +115,7 @@ export const CORE_DEFAULT_CONFIG: Pick<
     mecab: true,
     yomitanExtension: true,
     subtitleDictionaries: true,
-    jellyfinRemoteSession: true,
+    jellyfinRemoteSession: false,
   },
   updates: {
     enabled: true,