fix(audio): eliminate Android output stutter via Oboe config + lock-free callback (#20)

* fix(audio): eliminate Android output stutter via Oboe config + lock-free callback

Phase 1 — Oboe configuration:
- Change output stream from Usage::VoiceCommunication to Usage::Game with
  ContentType::Sonification to avoid forcing the Legacy (OpenSL ES) data
  path on most devices (Oboe issue #2075)
- Switch output format from i16 Mono to f32 Stereo, matching Qint's proven
  configuration and eliminating per-callback downmix conversion
- Set buffer size to 2x burst after stream open, reducing default buffer
  from 8-20x burst to 2x burst for lower latency
- Remove scratch Mutex<Vec<f32>>; callback writes directly to Oboe buffer

Phase 2 — Lock-free output callback:
- Add audio_event_queue.rs: lock-free SPSC bridge using crossbeam ArrayQueue
  with separate packet (lossy) and control (reliable) channels
- OutputCallback now owns AudioHandler directly (no Arc<Mutex<>> on Android)
- Inbound forwarder pushes packets via AudioEventProducer (no mutex)
- set_client_volume pushes control commands via event queue on Android
- iOS/desktop Arc<Mutex<AudioHandler>> path unchanged

* fix(audio): address PR #20 review findings

- Store AudioEventConsumer directly in OutputCallback to eliminate
  per-callback Arc clone on the real-time audio thread
- Add SAFETY comment for the unsafe from_raw_parts_mut transmute
- Bound set_client_volume spin-loop to 64 retries with warn log
- Remove redundant crossbeam-utils direct dependency
- Regenerate license inventory for new crossbeam deps (CI fix)

* fix(audio): use ASCII TODO punctuation

crates/chanora_audio/src/lib.rs

@@ -28,6 +28,8 @@
 
 #![warn(missing_docs)]
 
+#[cfg(target_os = "android")]
+mod audio_event_queue;
 pub mod audio_processing;
 pub mod debug_wav;
 mod engine;