- sounddevice InputStream at 44100Hz/512-sample blocks (~11.6ms latency)
- aubio.tempo beat detection with call_soon_threadsafe bridge (D-05)
- Thread-safe beat_count and bpm properties via threading.Lock (D-04)
- Double-trigger suppression with 200ms hold period
- ImportError wrapped in RuntimeError with clear message
- BeatDetector exported from led_sync.audio package
