- launcher/mpv.ts: state object, mpv IPC, process management, socket helpers
- launcher/youtube.ts: YouTube subtitle generation pipeline and helpers
- launcher/jellyfin.ts: Jellyfin API client, icon caching, play menu
- runAppCommandWithInherit and related functions placed in mpv.ts
- buildAppEnv deduplicated into single helper in mpv.ts
- launcher/types.ts: shared types, interfaces, and constants
- launcher/log.ts: logging infrastructure (COLORS, log, fail, etc.)
- launcher/util.ts: pure utilities, lang helpers, and child process runner
- runExternalCommand accepts childTracker param instead of referencing state
- inferWhisperLanguage placed in util.ts to avoid circular deps