7 TDD tasks: MusicLevel, MusicController+MusicBackend, Room music field, GameIO seams + loop/app wiring, Settings music level + SettingsMenu->GameIO refactor, OggMusicBackend + deps + SwingIO wiring + docs, backlog note. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>