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/ios_voice_unit.rs

@@ -549,7 +549,7 @@ impl IosVoiceUnit {
         let unit_arc2 = Arc::clone(&unit_arc);
 
         dispatch2::DispatchQueue::main().exec_async(move || {
-            let mut guard = unit_arc2.lock().unwrap();
+            let mut guard = unit_arc2.lock().unwrap_or_else(|e| e.into_inner());
             let unit = guard.as_mut().unwrap();
             let _ = tx.send(op(unit));
         });
@@ -559,7 +559,7 @@ impl IosVoiceUnit {
             Err(_) => Err("vpio lifecycle: main thread channel closed unexpectedly".to_string()),
         };
 
-        self.unit = unit_arc.lock().unwrap().take();
+        self.unit = unit_arc.lock().unwrap_or_else(|e| e.into_inner()).take();
         result.map_err(AudioError::Backend)
     }
 
@@ -1072,7 +1072,7 @@ impl IosVoiceUnit {
             let unit_arc2 = unit_arc.clone();
 
             dispatch2::DispatchQueue::main().exec_async(move || {
-                let mut guard = unit_arc2.lock().unwrap();
+                let mut guard = unit_arc2.lock().unwrap_or_else(|e| e.into_inner());
                 let u = guard.as_mut().unwrap();
                 let result = u
                     .initialize()
@@ -1094,7 +1094,7 @@ impl IosVoiceUnit {
                 }
             }
 
-            unit = unit_arc.lock().unwrap().take().unwrap();
+            unit = unit_arc.lock().unwrap_or_else(|e| e.into_inner()).take().unwrap();
         }
 
         info!(