fix(diag): record bridge and audio interruption diagnostics (#18)

* fix(diag): record bridge events in diagnostics page

Connection lost/reconnecting/disconnected and iOS audio interruption
events now appear in the diagnostics dialog alongside existing error
snackbar entries.

* fix(diag): reduce audio callback sample verbosity to debug

The render callback diagnostic sample logged every 100 callbacks
(~2s) at INFO level, flooding the 256-entry release log buffer and
pushing out useful events. Changed to DEBUG so it only appears in
debug builds with the larger 4096-entry buffer.

* fix(diag): add timestamps to Rust diagnostic log entries

apps/chanora_flutter/lib/main.dart

@@ -624,6 +624,7 @@ class _BetaHomeState extends State<_BetaHome> with WidgetsBindingObserver {
         });
         unawaited(_refreshSnapshot(recordActivity: false, reportErrors: true));
       case rust.BridgeEvent_Lost(:final reason):
+        _recordUiDiagnostic('connection', 'lost: $reason');
         setState(() {
           _phase = ConnectionPhase.reconnecting;
           _lostReason = reason;
@@ -631,12 +632,14 @@ class _BetaHomeState extends State<_BetaHome> with WidgetsBindingObserver {
           _reconnectDelay = null;
         });
       case rust.BridgeEvent_Reconnecting(:final attempt, :final delaySecs):
+        _recordUiDiagnostic('connection', 'reconnecting attempt=$attempt delay=${delaySecs}s');
         setState(() {
           _phase = ConnectionPhase.reconnecting;
           _reconnectAttempt = attempt;
           _reconnectDelay = delaySecs;
         });
       case rust.BridgeEvent_Disconnected():
+        _recordUiDiagnostic('connection', 'disconnected');
         setState(() {
           _resetConnectionUiState(phase: ConnectionPhase.disconnected);
         });
@@ -708,6 +711,7 @@ class _BetaHomeState extends State<_BetaHome> with WidgetsBindingObserver {
           if (!mounted) return;
           final messenger = ScaffoldMessenger.of(context);
           if (began) {
+            _recordUiDiagnostic('audio', 'interruption began');
             messenger.showSnackBar(
               SnackBar(
                 content: Text(AppL10n.of(context).iosAudioInterrupted),
@@ -716,6 +720,7 @@ class _BetaHomeState extends State<_BetaHome> with WidgetsBindingObserver {
               ),
             );
           } else if (shouldResume) {
+            _recordUiDiagnostic('audio', 'interruption ended, resuming');
             messenger.showSnackBar(
               SnackBar(
                 content: Text(AppL10n.of(context).iosAudioResuming),