## What changed
- Add `openDevices` and `setAudioControls` to the helper protocol. Open the default microphone and speaker after runtime initialization and transport negotiation, initially muted and suppressed.
- Use CPAL on macOS, GNU Linux, and MSVC Windows, with native audio dependencies confined to `codex-voice-host`. Add ALSA development dependencies to Linux CI.
- Pack callback samples into preallocated, bounded queues and service devices every 5 ms. Reject incompatible callback configurations, invalidate queued audio on control transitions, and reject capture backlog after unmute using device timestamps.
- Handle recoverable stream underruns and overruns without terminating the helper; terminate on device failure, active audio queue overflow, or stale queued audio.
Device opening only establishes local device readiness. Capture and rendered audio references are drained locally; encoding, decoding, and peer audio are not connected by this change.
## Testing
Add unit tests for mute boundaries, stale playback invalidation, sample bounds, partial-block packing and timestamps, callback size and timing limits, startup silence, queue overflow, and recoverable stream errors.
GitOrigin-RevId: 108aea3d411ef6c12908fe5fb67aaf9cddf4475f
Benjamin Carlsson
19b62211d9