addressed codex review cleanup

lib/screens/scanner_screen.dart

@@ -33,9 +33,12 @@ class _ScannerScreenState extends State<ScannerScreen> {
     _connector = Provider.of<MeshCoreConnector>(context, listen: false);
 
     _connectionListener = () {
+      final isCurrentRoute = ModalRoute.of(context)?.isCurrent ?? true;
       if (_connector.state == MeshCoreConnectionState.disconnected) {
         _changedNavigation = false;
       } else if (_connector.state == MeshCoreConnectionState.connected &&
+          _connector.activeTransport == MeshCoreTransportType.bluetooth &&
+          isCurrentRoute &&
           !_changedNavigation) {
         _changedNavigation = true;
         if (mounted) {

lib/services/usb_serial_service_native.dart

@@ -344,10 +344,6 @@ class UsbSerialService {
     // with a dangling NativeCallable pointer.
     if (_useDesktopFlSerial) {
       final serial = _serial;
-      _serial = null;
-      _status = UsbSerialStatus.disconnected;
-      _connectedPortKey = null;
-      _connectedPortLabel = null;
       try {
         if (serial?.isOpen() == FlOpenStatus.open) {
           serial?.closePort(); // synchronous C call — kills the SerialThread