Workstream A — poison-tolerant locking:
- Add utils/lock.rs with MutexSafe/RwLockSafe extension traits that recover a
poisoned std::sync lock instead of panicking, plus unit tests.
- Replace all 153 .lock().unwrap() and 4 .read()/.write().unwrap() production
sites with _safe variants across 14 files, eliminating the player
crash-cascade class. Tokio async mutexes are unchanged.
Workstream B — graceful backend init:
- create_player_backend no longer panics when MPV/ExoPlayer fail to initialize;
it falls back to NullBackend and emits a backend-init-failed event so the UI
can show "playback unavailable" instead of the app crashing. Fatal DB-setup
panics are kept.
Workstream F — doc reconciliation:
- Rewrite software-architecture.md's inaccurate "thin UI / ~800 lines" claims to
reflect reality (~20.5k non-test frontend) and document the events+polling
hybrid plus the new locking/backend-init behavior.
