fix: prevent duplicate AI design stream reconnects

tests/unit/image-workspace-store.test.ts

@@ -385,6 +385,20 @@ describe('AI design task event store', () => {
       .toEqual(['继续优化海报', '已完成最新方向整理。']);
   });
 
+  it('keeps the in-flight stream connection when reconciliation is requested', async () => {
+    const pendingSource = deferred<EventSource>();
+    openImageWorkspaceTaskEventsMock.mockReturnValue(pendingSource.promise);
+
+    await useImageWorkspaceStore.getState().load();
+    expect(useImageWorkspaceStore.getState().taskStreamState).toBe('connecting');
+    expect(openImageWorkspaceTaskEventsMock).toHaveBeenCalledOnce();
+
+    useImageWorkspaceStore.getState().markTaskStreamNeedsReconciliation();
+    useImageWorkspaceStore.getState().connectTaskStream();
+
+    expect(openImageWorkspaceTaskEventsMock).toHaveBeenCalledOnce();
+  });
+
   it('recovers a committed generation task when the Agent Run fails afterward', async () => {
     const source = new MockEventSource();
     openImageWorkspaceTaskEventsMock.mockResolvedValue(source as unknown as EventSource);