fix(audio): replace Mutex unwrap with poisoned-mutex recovery (TODO-006)

Replace 42 .lock().unwrap() calls with .unwrap_or_else(|e| e.into_inner())
across 7 files. Poisoned mutex recovery prevents panics in realtime audio
callbacks. Add SAFETY comment to WebRtcFallbackVad Send impl (TODO-007).

crates/chanora_audio/src/ptt_backends/macos.rs

@@ -543,7 +543,7 @@ impl DesktopPttBackend for MacOSEventTapBackend {
                 }
                 let runloop = unsafe { CFRunLoopGetCurrent() };
                 {
-                    let mut g = worker_runloop.lock().unwrap();
+                    let mut g = worker_runloop.lock().unwrap_or_else(|e| e.into_inner());
                     *g = Some(RunLoopHandle(runloop));
                 }
                 unsafe {