Handle BLE disconnection during active Omi recording

[unforced]

Problem

When an Omi device disconnects during an active recording, the app doesn't handle the disconnection gracefully. The recording data could be lost without user notification.

Location: lib/services/omi/omi_capture_service.dart:162-168

void _onAudioData(List<int> data) {
  if (!_isRecording || _wavBytesUtil == null) return;
  _wavBytesUtil!.storeFramePacket(data);
}

Expected Behavior

When device disconnects mid-recording:

1. Detect the disconnection event
2. Save partial recording (what was captured so far)
3. Notify user with clear message
4. Mark recording metadata to indicate it was incomplete

Suggested Implementation

// In OmiCaptureService
StreamSubscription? _disconnectListener;

Future<void> startListening() async {
  // Listen for disconnections
  _disconnectListener = bluetoothService.connectionStateStream
    .where((state) => state == DeviceConnectionState.disconnected)
    .listen((_) => _handleUnexpectedDisconnect());
}

Future<void> _handleUnexpectedDisconnect() async {
  if (_isRecording) {
    debugPrint('[OmiCaptureService] Device disconnected during recording');
    
    // Save partial recording
    await _stopRecordingWithTapCount(_currentButtonTapCount ?? 1);
    
    // Notify user
    onStatusMessage?.call('Device disconnected - partial recording saved');
  }
}

Benefits

• No data loss on unexpected disconnection
• Better user experience with clear feedback
• Partial recordings can still be useful

Priority

High - Affects user data integrity

Related

• Part of PR #8 review feedback
• Related to BLE connection stability