feat: smarter firmware confirm via reconnect

test/service/firmware_update_service_test.dart

@@ -140,6 +140,89 @@ void main() {
       await transport.dispose();
     });
 
+    test('completes when FINISH status is lost but bootloader disconnects',
+        () async {
+      final image = _validImage(80);
+      final transport = _FakeFirmwareUpdateTransport(
+        totalBytes: image.length,
+        suppressFinishStatus: true,
+      );
+      final service = FirmwareUpdateService(
+        transport: transport,
+        defaultStatusTimeout: const Duration(milliseconds: 20),
+        defaultPostFinishResetTimeout: const Duration(milliseconds: 100),
+      );
+
+      final result = await service.startUpdate(
+        imageBytes: image,
+        sessionId: 15,
+      );
+
+      expect(result.isOk(), isTrue);
+      expect(
+          transport.controlWrites.last, [universalShifterDfuOpcodeFinish, 15]);
+      expect(transport.steps, contains('reconnectForVerification'));
+      expect(transport.steps, contains('verifyDeviceReachable'));
+      expect(service.currentProgress.state, DfuUpdateState.completed);
+
+      await service.dispose();
+      await transport.dispose();
+    });
+
+    test('fails when FINISH status is lost and bootloader stays connected',
+        () async {
+      final image = _validImage(80);
+      final transport = _FakeFirmwareUpdateTransport(
+        totalBytes: image.length,
+        suppressFinishStatus: true,
+        disconnectAfterFinish: false,
+      );
+      final service = FirmwareUpdateService(
+        transport: transport,
+        defaultStatusTimeout: const Duration(milliseconds: 10),
+        defaultPostFinishResetTimeout: const Duration(milliseconds: 30),
+      );
+
+      final result = await service.startUpdate(
+        imageBytes: image,
+        sessionId: 16,
+      );
+
+      expect(result.isErr(), isTrue);
+      expect(result.unwrapErr().toString(), contains('post-FINISH reset'));
+      expect(service.currentProgress.state, DfuUpdateState.failed);
+      expect(transport.steps, isNot(contains('reconnectForVerification')));
+
+      await service.dispose();
+      await transport.dispose();
+    });
+
+    test('fails when FINISH returns explicit bootloader error', () async {
+      final image = _validImage(80);
+      final transport = _FakeFirmwareUpdateTransport(
+        totalBytes: image.length,
+        finishStatusCode: DfuBootloaderStatusCode.flashError,
+      );
+      final service = FirmwareUpdateService(
+        transport: transport,
+        defaultStatusTimeout: const Duration(milliseconds: 20),
+        defaultPostFinishResetTimeout: const Duration(milliseconds: 100),
+      );
+
+      final result = await service.startUpdate(
+        imageBytes: image,
+        sessionId: 17,
+      );
+
+      expect(result.isErr(), isTrue);
+      expect(result.unwrapErr().toString(), contains('flash error'));
+      expect(service.currentProgress.state, DfuUpdateState.failed);
+      expect(transport.steps, isNot(contains('reconnectForVerification')));
+
+      await service.dispose();
+      await transport.dispose();
+    });
+
     test('reconnects and resumes from status after transient data failure',
         () async {
       final image = _validImage(130);
@@ -297,6 +380,9 @@ class _FakeFirmwareUpdateTransport implements FirmwareUpdateTransport {
     this.suppressFirstDataStatus = false,
     this.failDataWriteAtOffsetOnce,
     this.resetSessionOnRecoveryStatus = false,
+    this.suppressFinishStatus = false,
+    this.disconnectAfterFinish = true,
+    this.finishStatusCode = DfuBootloaderStatusCode.ok,
     this.onDataWrite,
   });
 
@@ -308,6 +394,9 @@ class _FakeFirmwareUpdateTransport implements FirmwareUpdateTransport {
   final bool suppressFirstDataStatus;
   final int? failDataWriteAtOffsetOnce;
   final bool resetSessionOnRecoveryStatus;
+  final bool suppressFinishStatus;
+  final bool disconnectAfterFinish;
+  final DfuBootloaderStatusCode finishStatusCode;
   final void Function()? onDataWrite;
 
   final StreamController<List<int>> _statusController =
@@ -323,6 +412,7 @@ class _FakeFirmwareUpdateTransport implements FirmwareUpdateTransport {
   bool _sentDataFailure = false;
   bool _sentQueueFull = false;
   bool _suppressedDataStatus = false;
+  bool _finishDisconnectAvailable = false;
 
   @override
   Future<Result<bool>> isConnectedToBootloader() async {
@@ -389,7 +479,11 @@ class _FakeFirmwareUpdateTransport implements FirmwareUpdateTransport {
       }
       _scheduleStatus(DfuBootloaderStatusCode.ok, _sessionId, _expectedOffset);
     } else if (opcode == universalShifterDfuOpcodeFinish) {
-      _scheduleStatus(DfuBootloaderStatusCode.ok, payload[1], totalBytes);
+      if (suppressFinishStatus) {
+        _finishDisconnectAvailable = disconnectAfterFinish;
+      } else {
+        _scheduleStatus(finishStatusCode, payload[1], totalBytes);
+      }
     } else if (opcode == universalShifterDfuOpcodeAbort) {
       _scheduleStatus(DfuBootloaderStatusCode.ok, payload[1], 0);
     }
@@ -431,7 +525,11 @@ class _FakeFirmwareUpdateTransport implements FirmwareUpdateTransport {
   @override
   Future<Result<void>> waitForBootloaderDisconnect(
       {required Duration timeout}) async {
+    if (timeout == Duration.zero && !_finishDisconnectAvailable) {
+      return bail('still connected');
+    }
     steps.add('waitForBootloaderDisconnect');
+    _finishDisconnectAvailable = true;
     return Ok(null);
   }