Add rejected mutation requeue flow in sync UI

test/features/sync/sync_queue_repository_test.dart

@@ -67,6 +67,7 @@ void main() {
       expect(state.pending, isEmpty);
       expect(state.cursor, 'cursor-2');
       expect(state.rejected.length, 1);
+      expect(state.rejectedChanges.length, 1);
       expect(state.lastError, contains('Push rejected'));
     },
   );
@@ -104,9 +105,52 @@ void main() {
       await notifier.clearRejections();
       final SyncStateData state = await _readState(container);
       expect(state.rejected, isEmpty);
+      expect(state.rejectedChanges, isEmpty);
       expect(state.lastError, isNull);
     },
   );
+
+  test(
+    'requeueRejectedChanges adds rejected envelopes back to pending',
+    () async {
+      final ProviderContainer container = ProviderContainer(
+        overrides: [
+          syncStateStoreProvider.overrideWithValue(InMemorySyncStateStore()),
+        ],
+      );
+      addTearDown(container.dispose);
+
+      final SyncQueueRepository notifier = container.read(
+        syncQueueRepositoryProvider.notifier,
+      );
+
+      await notifier.enqueue(_change(id: 'p-9', mutationId: 'cm-x'));
+      await notifier.applyPushResult(
+        SyncPushResult(
+          cursor: 'cursor-10',
+          accepted: const <MutationAck>[],
+          rejected: const <MutationRejection>[
+            MutationRejection(
+              clientMutationId: 'cm-x',
+              code: 'VALIDATION_FAILED',
+              message: 'invalid payload',
+            ),
+          ],
+        ),
+      );
+
+      SyncStateData state = await _readState(container);
+      expect(state.pending, isEmpty);
+      expect(state.rejectedChanges.length, 1);
+
+      await notifier.requeueRejectedChanges();
+      state = await _readState(container);
+      expect(state.pending.length, 1);
+      expect(state.pending.first.clientMutationId, 'cm-x');
+      expect(state.rejected, isEmpty);
+      expect(state.rejectedChanges, isEmpty);
+    },
+  );
 }
 
 class SyncStateData {
@@ -114,12 +158,14 @@ class SyncStateData {
     required this.cursor,
     required this.pending,
     required this.rejected,
+    required this.rejectedChanges,
     required this.lastError,
   });
 
   final String? cursor;
   final List<ChangeEnvelope> pending;
   final List<MutationRejection> rejected;
+  final List<ChangeEnvelope> rejectedChanges;
   final String? lastError;
 }
 
@@ -129,6 +175,7 @@ Future<SyncStateData> _readState(ProviderContainer container) async {
     cursor: state.cursor,
     pending: state.pendingChanges,
     rejected: state.lastRejected,
+    rejectedChanges: state.lastRejectedChanges,
     lastError: state.lastError,
   );
 }