保存标注前预检陈旧id

- dirty 标注保存前拉取后端标注 id 列表，已缺失的本地旧 annotationId 直接重新创建

- 保留 PATCH 404 兜底，覆盖预检后并发删除的情况

- 扩充分割工作区测试，区分预检缺失和 PATCH 后缺失两条路径

- 同步更新接口契约、需求冻结、设计冻结、测试计划和 AGENTS 说明

src/components/VideoWorkspace.test.tsx

@@ -387,6 +387,10 @@ describe('VideoWorkspace', () => {
     apiMock.getProjectFrames.mockResolvedValueOnce([
       { id: 10, project_id: 1, frame_index: 0, image_url: '/frame.jpg', width: 640, height: 360 },
     ]);
+    apiMock.getProjectAnnotations
+      .mockResolvedValueOnce([])
+      .mockResolvedValueOnce([{ id: 99, frame_id: 10 }])
+      .mockResolvedValueOnce([]);
     apiMock.buildAnnotationPayload.mockReturnValueOnce({
       project_id: 1,
       frame_id: 10,
@@ -445,11 +449,12 @@ describe('VideoWorkspace', () => {
     expect(apiMock.saveAnnotation).not.toHaveBeenCalled();
   });
 
-  it('recreates a dirty local annotation when the backend PATCH target is already missing', async () => {
+  it('recreates a dirty local annotation without PATCH when the backend preflight says it is missing', async () => {
     apiMock.getProjectFrames.mockResolvedValueOnce([
       { id: 10, project_id: 1, frame_index: 0, image_url: '/frame.jpg', width: 640, height: 360 },
     ]);
     apiMock.getProjectAnnotations
+      .mockResolvedValueOnce([])
       .mockResolvedValueOnce([])
       .mockResolvedValueOnce([{ id: 120, frame_id: 10 }]);
     apiMock.annotationToMask.mockImplementation((annotation) => ({
@@ -469,7 +474,6 @@ describe('VideoWorkspace', () => {
       template_id: 2,
       mask_data: { polygons: [], label: '胆囊' },
     });
-    apiMock.updateAnnotation.mockRejectedValueOnce({ response: { status: 404 } });
     apiMock.saveAnnotation.mockResolvedValueOnce({ id: 120 });
 
     render(<VideoWorkspace />);
@@ -497,9 +501,8 @@ describe('VideoWorkspace', () => {
 
     fireEvent.click(screen.getByRole('button', { name: '保存 1 个改动' }));
 
-    await waitFor(() => expect(apiMock.updateAnnotation).toHaveBeenCalledWith('11859', expect.objectContaining({
-      template_id: 2,
-    })));
+    await waitFor(() => expect(apiMock.saveAnnotation).toHaveBeenCalled());
+    expect(apiMock.updateAnnotation).not.toHaveBeenCalled();
     expect(apiMock.saveAnnotation).toHaveBeenCalledWith({
       project_id: 1,
       frame_id: 10,
@@ -518,6 +521,68 @@ describe('VideoWorkspace', () => {
     expect(screen.getByText('已保存 1 个标注，其中 1 个本地旧标注已重新创建')).toBeInTheDocument();
   });
 
+  it('recreates a dirty local annotation if the backend PATCH target disappears after preflight', async () => {
+    apiMock.getProjectFrames.mockResolvedValueOnce([
+      { id: 10, project_id: 1, frame_index: 0, image_url: '/frame.jpg', width: 640, height: 360 },
+    ]);
+    apiMock.getProjectAnnotations
+      .mockResolvedValueOnce([])
+      .mockResolvedValueOnce([{ id: 11859, frame_id: 10 }])
+      .mockResolvedValueOnce([{ id: 121, frame_id: 10 }]);
+    apiMock.annotationToMask.mockImplementation((annotation) => ({
+      id: `annotation-${annotation.id}`,
+      annotationId: String(annotation.id),
+      frameId: String(annotation.frame_id),
+      pathData: 'M 0 0 Z',
+      label: '胆囊',
+      color: '#ff0000',
+      saved: true,
+      saveStatus: 'saved',
+      segmentation: [[0, 0, 10, 0, 10, 10]],
+    }));
+    apiMock.buildAnnotationPayload.mockReturnValueOnce({
+      project_id: 1,
+      frame_id: 10,
+      template_id: 2,
+      mask_data: { polygons: [], label: '胆囊' },
+    });
+    apiMock.updateAnnotation.mockRejectedValueOnce({ response: { status: 404 } });
+    apiMock.saveAnnotation.mockResolvedValueOnce({ id: 121 });
+
+    render(<VideoWorkspace />);
+    await waitFor(() => expect(useStore.getState().frames).toHaveLength(1));
+    act(() => {
+      useStore.setState({
+        activeTemplateId: '2',
+        masks: [{
+          id: 'annotation-11859',
+          annotationId: '11859',
+          frameId: '10',
+          pathData: 'M 0 0 Z',
+          label: '胆囊',
+          color: '#ff0000',
+          saveStatus: 'dirty',
+          segmentation: [[0, 0, 10, 0, 10, 10]],
+        }],
+      });
+    });
+
+    fireEvent.click(screen.getByRole('button', { name: '保存 1 个改动' }));
+
+    await waitFor(() => expect(apiMock.updateAnnotation).toHaveBeenCalledWith('11859', expect.objectContaining({
+      template_id: 2,
+    })));
+    expect(apiMock.saveAnnotation).toHaveBeenCalledWith({
+      project_id: 1,
+      frame_id: 10,
+      template_id: 2,
+      mask_data: { polygons: [], label: '胆囊' },
+    });
+    await waitFor(() => expect(useStore.getState().masks).toEqual([
+      expect.objectContaining({ id: 'annotation-121', annotationId: '121', saveStatus: 'saved' }),
+    ]));
+  });
+
   it('deletes saved annotations when clearing current-frame masks', async () => {
     apiMock.getProjectFrames.mockResolvedValueOnce([
       { id: 10, project_id: 1, frame_index: 0, image_url: '/frame.jpg', width: 640, height: 360 },

src/components/VideoWorkspace.tsx

@@ -767,11 +767,27 @@ export function VideoWorkspace({ onNavigateToAI }: { onNavigateToAI?: () => void
         return 0;
       }
 
+      let existingAnnotationIds: Set<string> | null = null;
+      if (updateItems.length > 0) {
+        try {
+          const annotations = await getProjectAnnotations(currentProject.id);
+          existingAnnotationIds = new Set(annotations.map((annotation) => String(annotation.id)));
+        } catch {
+          existingAnnotationIds = null;
+        }
+      }
+
       let recreatedMissingCount = 0;
       const recreatedMaskIds: string[] = [];
       await Promise.all([
         ...createItems.map(({ payload }) => saveAnnotation(payload)),
         ...updateItems.map(async ({ maskId, annotationId, updatePayload, createPayload }) => {
+          if (existingAnnotationIds && !existingAnnotationIds.has(String(annotationId))) {
+            recreatedMissingCount += 1;
+            recreatedMaskIds.push(maskId);
+            await saveAnnotation(createPayload);
+            return;
+          }
           try {
             await updateAnnotation(annotationId, updatePayload);
           } catch (error) {