feat: snackbar for flash err + disconnect on dfurecovery end

test/service/firmware_update_service_test.dart

@@ -333,6 +333,35 @@ void main() {
       await transport.dispose();
     });
 
+    test('fails early on boot metadata error before START', () async {
+      final image = _validImage(40);
+      final transport = _FakeFirmwareUpdateTransport(
+        totalBytes: image.length,
+        initialStatusCode: DfuBootloaderStatusCode.bootMetadataError,
+      );
+      final service = FirmwareUpdateService(
+        transport: transport,
+        defaultStatusTimeout: const Duration(milliseconds: 100),
+      );
+
+      final result = await service.startUpdate(
+        imageBytes: image,
+        sessionId: 18,
+      );
+
+      expect(result.isErr(), isTrue);
+      expect(result.unwrapErr().toString(),
+          startsWith(universalShifterBootMetadataWarningMessage));
+      expect(
+          transport.controlWrites
+              .where((write) => write.first == universalShifterDfuOpcodeStart),
+          isEmpty);
+      expect(service.currentProgress.state, DfuUpdateState.failed);
+
+      await service.dispose();
+      await transport.dispose();
+    });
+
     test('cancel after START sends session-scoped ABORT', () async {
       final image = _validImage(80);
       final firstFrameSent = Completer<void>();
@@ -373,6 +402,7 @@ void main() {
 class _FakeFirmwareUpdateTransport implements FirmwareUpdateTransport {
   _FakeFirmwareUpdateTransport({
     required this.totalBytes,
+    this.initialStatusCode = DfuBootloaderStatusCode.ok,
     this.startStatusCode = DfuBootloaderStatusCode.ok,
     this.alreadyInBootloader = false,
     this.failEnterBootloader = false,
@@ -387,6 +417,7 @@ class _FakeFirmwareUpdateTransport implements FirmwareUpdateTransport {
   });
 
   final int totalBytes;
+  final DfuBootloaderStatusCode initialStatusCode;
   final DfuBootloaderStatusCode startStatusCode;
   final bool alreadyInBootloader;
   final bool failEnterBootloader;
@@ -461,7 +492,7 @@ class _FakeFirmwareUpdateTransport implements FirmwareUpdateTransport {
   @override
   Future<Result<List<int>>> readStatus() async {
     steps.add('readStatus');
-    return Ok(_status(DfuBootloaderStatusCode.ok, 0, 0));
+    return Ok(_status(initialStatusCode, 0, 0));
   }
 
   @override