feat(macos): add macOS audio lifecycle MethodChannel

apps/chanora_flutter/macos/Runner/MacOSAudioLifecycle.swift (new): native MethodChannel handler for chanora/macos_audio_lifecycle. Observes Core Audio HAL default-input and default-output device property changes via AudioObjectAddPropertyListener; posts handleDefaultDeviceChange events with {role: input|output} payload. Mirrors the iOS chanora/ios_audio_lifecycle event surface minus the AVAudioSession-specific events (no interruption / no media services reset equivalents on macOS — no AVAudioSession).

apps/chanora_flutter/macos/Runner/MainFlutterWindow.swift: register MacOSAudioLifecycle next to MacOSPermissionsHandler in awakeFromNib. Closes the iOS/macOS asymmetry noted in SysRS-051.

apps/chanora_flutter/lib/services/audio_lifecycle_service.dart: add wireMacosAudioLifecycle() parallel to wireIosAudioLifecycle() / wireAndroidAudioLifecycle(). The current implementation captures and logs the events; the FRB function that triggers a VPIO re-bind on the engine is a follow-up. Event-shape mirrors the iOS side so a future caller can switch on platform without changing the dispatch shape.

apps/chanora_flutter/test/services/audio_lifecycle_service_test.dart: smoke test for wireMacosAudioLifecycle (4 tests pass, including the new one).

apps/chanora_flutter/macos/Runner/MainFlutterWindow.swift

@@ -399,6 +399,8 @@ class MainFlutterWindow: NSWindow {
 
     // Register the macOS permissions MethodChannel handler.
     MacOSPermissionsHandler.register(with: flutterViewController.registrar(forPlugin: "MacOSPermissionsHandler"))
+    // Register the macOS audio-lifecycle MethodChannel handler (closes the iOS/macOS asymmetry in SysRS-051).
+    MacOSAudioLifecycle.register(with: flutterViewController.registrar(forPlugin: "MacOSAudioLifecycle"))
 
     super.awakeFromNib()
   }