feat(audio,bridge,flutter): v1 audio + PTT lifecycle implementation (SDD-094..097)

Implement the SDD-094 / SDD-095 / SDD-096 / SDD-097 detailed designs
committed in dfa84ee.

Rust side
- chanora_audio::TransmitMode enum (Ptt/Continuous/VoiceActivity) with
  serde-friendly u8 repr (SDD-095).
- chanora_audio::TransmitModeSelector: lock-free Atomic-backed selector
  that is the sole writer of transmit_active (per SAD-083), applying
  hard_mute as a final clamp. VoiceActivity falls through to Continuous
  for v1 (DEC-030 placeholder).
- chanora_audio::ReleaseTailTimer: tokio-task-owning struct driving the
  selector's ptt_held input; default 200 ms tail, configurable 0–500 ms
  with AtomicU32 hot read; pending JoinHandle held in a std::sync::Mutex
  touched only on PTT edge transitions (SDD-096).
- chanora_storage: AudioMeta persisted as audio_meta.json next to
  identity.dek; get/set_transmit_mode + get/set_release_tail_ms with
  0..=500 clamp on write.
- chanora_core::ChanoraSession: voice_join(channel, password) and
  voice_leave() are the new lifecycle entry points; ensure_audio_running
  and shutdown_audio_if_idle are private helpers around the existing
  Option<AudioEngine> field. SessionEvent::VoiceState carries the
  in_channel / transmit_mode / mute / release_tail_ms tuple. Selector
  state survives reconnect; supervisor rewires it to each fresh engine
  gate.
- chanora_bridge: drop start_audio; add voice_join, voice_leave,
  set/get_transmit_mode, set/get_release_tail_ms, set_hard_mute.
  BridgeEvent::VoiceState mirrors the core event. AudioStarted/Stopped
  kept for backwards compat but Flutter ignores them in the new UI.

Flutter side
- New apps/chanora_flutter/lib/widgets/voice_bar.dart replaces the
  legacy _AudioControls widget. Renders channel pill, mode badge,
  mute toggle, level meter, PttCapabilityBadge, leave button. No
  manual Start affordance anywhere.
- New apps/chanora_flutter/lib/widgets/voice_settings.dart dialog with
  TransmitMode radio group (VoiceActivity disabled with 'Coming soon'
  trailing label per DEC-030), bind-key button, release-tail slider
  0–500 ms step 25.
- main.dart: state fields _inChannel, _transmitMode, _hardMute,
  _releaseTailMs driven by BridgeEvent_VoiceState. Channel-tap now
  calls voiceJoin instead of moveToChannel. Removed _onStartAudio,
  _audioStarted-gated branch, and the FilledButton.
- l10n: 11 new strings in app_en.arb + app_zh.arb.

Verification
- cargo check --workspace: clean.
- cargo test --workspace --lib: 72 passed / 0 failed / 1 ignored
  (chanora_audio: +12 new tests for TransmitMode/Selector/ReleaseTail;
  chanora_storage: +2 new tests for audio_meta round-trip).
- flutter analyze: 0 errors, 0 warnings; 6 infos are the Flutter 3.32
  Radio.groupValue deprecation (pre-existing API usage).
- FRB Dart/Rust bindings regenerated via flutter_rust_bridge_codegen.

Follow-up (intentionally deferred)
- PttController and per-platform PTT backends still drive AudioTransmitGate
  directly via the legacy set_ptt path; routing those key edges through
  ChanoraSession::release_tail_timer().{key_down,key_up} so the tail
  applies to native PTT input is a contained wiring change in a follow-up.
- Real audio-level RMS in BridgeAudioStats (current meter is binary).
- VoiceActivity backend (DEC-030).

apps/chanora_flutter/lib/main.dart

@@ -19,6 +19,8 @@ import 'package:path_provider/path_provider.dart';
 import 'l10n/generated/app_localizations.dart';
 import 'src/rust/api.dart' as rust;
 import 'src/rust/frb_generated.dart';
+import 'widgets/voice_bar.dart';
+import 'widgets/voice_settings.dart';
 
 /// Public version string shown in the About dialog. Aligned with
 /// `pubspec.yaml` and the git tag for the MVP release candidate.
@@ -95,17 +97,27 @@ class _BetaHomeState extends State<_BetaHome> {
   _Phase _phase = _Phase.idle;
   rust.BridgeSnapshot? _snapshot;
   String? _error;
+  // ignore: unused_field
   bool _audioStarted = false;
   rust.BridgeAudioStats? _audioStats;
   Timer? _statsTimer;
   StreamSubscription<rust.BridgeEvent>? _eventsSub;
 
+  // v1 voice subsystem state (SDD-094/095/096/097). Driven by
+  // BridgeEvent::VoiceState.
+  bool _inChannel = false;
+  rust.BridgeTransmitMode _transmitMode = rust.BridgeTransmitMode.ptt;
+  bool _hardMute = false;
+  int _releaseTailMs = 200;
+  BigInt? _currentVoiceChannelId;
+
   String? _lostReason;
   int? _reconnectAttempt;
   int? _reconnectDelay;
 
   bool _inputMuted = false;
   bool _outputMuted = false;
+  // ignore: unused_field
   double _outputGain = 1.0;
 
   // Desktop PTT capability badge state (gen2 v0.9.3 / SDD-091).
@@ -189,9 +201,39 @@ class _BetaHomeState extends State<_BetaHome> {
           _pttBackendId = backendId;
           _pttBoundInputClass = boundInputClass;
         });
+      case rust.BridgeEvent_VoiceState(
+            :final inChannel,
+            :final transmitMode,
+            :final mute,
+            :final releaseTailMs,
+          ):
+        setState(() {
+          _inChannel = inChannel;
+          _transmitMode = transmitMode;
+          _hardMute = mute;
+          _releaseTailMs = releaseTailMs;
+          _audioStarted = inChannel;
+        });
+        if (inChannel) {
+          _ensureStatsTimer();
+        } else {
+          _statsTimer?.cancel();
+          _statsTimer = null;
+        }
     }
   }
 
+  void _ensureStatsTimer() {
+    if (_statsTimer != null) return;
+    _statsTimer = Timer.periodic(const Duration(milliseconds: 500), (_) async {
+      try {
+        final s = await rust.audioStats();
+        if (!mounted) return;
+        setState(() => _audioStats = s);
+      } catch (_) {}
+    });
+  }
+
   @override
   void dispose() {
     _eventsSub?.cancel();
@@ -232,25 +274,7 @@ class _BetaHomeState extends State<_BetaHome> {
     }
   }
 
-  Future<void> _onStartAudio() async {
-    try {
-      await rust.startAudio();
-      if (!mounted) return;
-      setState(() => _audioStarted = true);
-      _statsTimer?.cancel();
-      _statsTimer = Timer.periodic(const Duration(milliseconds: 500), (_) async {
-        try {
-          final s = await rust.audioStats();
-          if (!mounted) return;
-          setState(() => _audioStats = s);
-        } catch (_) {}
-      });
-    } catch (e) {
-      if (!mounted) return;
-      setState(() => _error = e.toString());
-    }
-  }
-
+  // ignore: unused_element
   Future<void> _setPtt(bool active) async {
     try {
       await rust.setPtt(active: active);
@@ -260,6 +284,7 @@ class _BetaHomeState extends State<_BetaHome> {
     }
   }
 
+  // ignore: unused_element
   Future<void> _toggleInputMute() async {
     final next = !_inputMuted;
     try {
@@ -272,6 +297,7 @@ class _BetaHomeState extends State<_BetaHome> {
     }
   }
 
+  // ignore: unused_element
   Future<void> _toggleOutputMute() async {
     final next = !_outputMuted;
     try {
@@ -284,6 +310,7 @@ class _BetaHomeState extends State<_BetaHome> {
     }
   }
 
+  // ignore: unused_element
   Future<void> _setOutputGain(double value) async {
     setState(() => _outputGain = value);
     try {
@@ -303,16 +330,60 @@ class _BetaHomeState extends State<_BetaHome> {
       if (password == null) return; // cancelled
     }
     try {
-      await rust.moveToChannel(
+      await rust.voiceJoin(
         channelId: ch.id,
         password: password ?? '',
       );
+      if (!mounted) return;
+      setState(() => _currentVoiceChannelId = ch.id);
     } catch (e) {
       if (!mounted) return;
       setState(() => _error = e.toString());
     }
   }
 
+  Future<void> _onLeaveVoice() async {
+    try {
+      await rust.voiceLeave();
+      if (!mounted) return;
+      setState(() => _currentVoiceChannelId = null);
+    } catch (e) {
+      if (!mounted) return;
+      setState(() => _error = e.toString());
+    }
+  }
+
+  Future<void> _onToggleHardMute() async {
+    final next = !_hardMute;
+    try {
+      await rust.setHardMute(muted: next);
+    } catch (e) {
+      if (!mounted) return;
+      setState(() => _error = e.toString());
+    }
+  }
+
+  Future<void> _onOpenVoiceSettings() async {
+    final result = await showDialog<VoiceSettingsResult>(
+      context: context,
+      builder: (ctx) => VoiceSettingsDialog(
+        initialMode: _transmitMode,
+        initialReleaseTailMs: _releaseTailMs,
+      ),
+    );
+    if (result == null) return;
+    try {
+      await rust.setTransmitMode(mode: result.mode);
+      await rust.setReleaseTailMs(ms: result.releaseTailMs);
+    } catch (e) {
+      if (!mounted) return;
+      setState(() => _error = e.toString());
+    }
+    if (result.bindKeyRequested && mounted) {
+      await _onConfigurePtt(context);
+    }
+  }
+
   Future<String?> _askChannelPassword(AppL10n l10n) async {
     final ctl = TextEditingController();
     final result = await showDialog<String>(
@@ -367,9 +438,21 @@ class _BetaHomeState extends State<_BetaHome> {
       _error = null;
       _inputMuted = false;
       _outputMuted = false;
+      _inChannel = false;
+      _currentVoiceChannelId = null;
     });
   }
 
+  String _currentVoiceChannelName() {
+    final id = _currentVoiceChannelId;
+    final snap = _snapshot;
+    if (id == null || snap == null) return '';
+    for (final ch in snap.channels) {
+      if (ch.id == id) return ch.name;
+    }
+    return '';
+  }
+
   Future<void> _onShowDiagnostics(BuildContext context) async {
     final l10n = AppL10n.of(context);
     final text = rust.exportDiagnostics();
@@ -726,32 +809,22 @@ class _BetaHomeState extends State<_BetaHome> {
                 ),
               ),
             ] else if (_phase == _Phase.connected && _snapshot != null) ...[
-              if (!_audioStarted) ...[
-                FilledButton.icon(
-                  icon: const Icon(Icons.mic_none),
-                  label: Text(l10n.startAudioAction),
-                  onPressed: _onStartAudio,
-                ),
-                const SizedBox(height: 12),
-              ] else ...[
-                _AudioControls(
-                  stats: _audioStats,
-                  inputMuted: _inputMuted,
-                  outputMuted: _outputMuted,
-                  outputGain: _outputGain,
-                  pttLevel: _pttLevel,
-                  pttBackendId: _pttBackendId,
-                  pttBoundInputClass: _pttBoundInputClass,
-                  pttBoundKeyLabel: _pttBoundKeyLabel,
-                  onPttDown: () => _setPtt(true),
-                  onPttUp: () => _setPtt(false),
-                  onToggleInputMute: _toggleInputMute,
-                  onToggleOutputMute: _toggleOutputMute,
-                  onGainChanged: _setOutputGain,
-                  onConfigurePtt: () => _onConfigurePtt(context),
-                ),
-                const SizedBox(height: 12),
-              ],
+              VoiceBar(
+                inChannel: _inChannel,
+                transmitMode: _transmitMode,
+                hardMute: _hardMute,
+                releaseTailMs: _releaseTailMs,
+                channelName: _currentVoiceChannelName(),
+                audioStats: _audioStats,
+                pttLevel: _pttLevel,
+                pttBackendId: _pttBackendId,
+                pttBoundInputClass: _pttBoundInputClass,
+                pttBoundKeyLabel: _pttBoundKeyLabel,
+                onToggleMute: _onToggleHardMute,
+                onConfigure: _onOpenVoiceSettings,
+                onLeave: _onLeaveVoice,
+              ),
+              const SizedBox(height: 12),
               Expanded(
                 child: _SnapshotView(
                   snapshot: _snapshot!,