* fix: reduce audio jitter buffer latency
- Release listenersMu before dispatching samples to listeners
- Buffer Track.sample channel (size 2) with non-blocking WriteSample
- Buffer pipeline.sample channel (size 4) to unblock GStreamer thread
- Add leaky=downstream max-size-buffers=5 to audio queue to prevent burst accumulation
- Set sync=false on appsink to deliver buffers immediately without clock wait
These changes break the backpressure chain that caused the GStreamer
streaming thread to stall. When the Go scheduler has a hiccup, buffered
frames were delivered in a burst, causing the browser audio jitter buffer
to grow to ~10 seconds over time.
Fixes: #598
* fix: log message when dropping samples due to full track channel
Miroslav Šedivý