生成帧完成后自动刷新项目封面

- 项目库生成帧任务入队后继续轮询任务进度，解析成功后重新拉取项目列表和当前项目对象。

- 成功后显示视频帧生成完成提示，并让后端写入的 thumbnail_url 立即刷新到项目卡片封面。

- 补充 ProjectLibrary 回归测试，覆盖生成帧完成后自动显示新封面。

- 更新前端审计、设计冻结、测试计划、状态机和项目指南文档。

src/components/ProjectLibrary.test.tsx

@@ -134,8 +134,10 @@ describe('ProjectLibrary', () => {
   it('generates frames from an imported video with the selected FPS', async () => {
     apiMock.getProjects
       .mockResolvedValueOnce([{ id: 'p4', name: 'clip.mp4', status: 'pending', frames: 0, video_path: 'uploads/clip.mp4', parse_fps: 30 }])
-      .mockResolvedValueOnce([{ id: 'p4', name: 'clip.mp4', status: 'parsing', frames: 0, video_path: 'uploads/clip.mp4', parse_fps: 12 }]);
+      .mockResolvedValueOnce([{ id: 'p4', name: 'clip.mp4', status: 'parsing', frames: 0, video_path: 'uploads/clip.mp4', parse_fps: 12 }])
+      .mockResolvedValueOnce([{ id: 'p4', name: 'clip.mp4', status: 'ready', frames: 24, video_path: 'uploads/clip.mp4', parse_fps: 12, thumbnail_url: 'http://thumb/frame.jpg' }]);
     apiMock.parseMedia.mockResolvedValueOnce({ id: 22, status: 'queued', progress: 0 });
+    apiMock.getTask.mockResolvedValueOnce({ id: 22, status: 'success', progress: 100, message: '解析完成' });
 
     const { container } = render(<ProjectLibrary onProjectSelect={vi.fn()} />);
 
@@ -146,6 +148,11 @@ describe('ProjectLibrary', () => {
     await waitFor(() => expect(apiMock.parseMedia).toHaveBeenCalledWith('p4', { parseFps: 12 }));
     expect(await screen.findByRole('status')).toHaveTextContent('生成帧任务已入队 #22');
     expect(await screen.findByText('12FPS')).toBeInTheDocument();
+    expect(screen.getByText('正在生成视频帧')).toBeInTheDocument();
+
+    await waitFor(() => expect(apiMock.getTask).toHaveBeenCalledWith(22), { timeout: 2500 });
+    expect(await screen.findByAltText('clip.mp4')).toHaveAttribute('src', 'http://thumb/frame.jpg');
+    expect(await screen.findByRole('status')).toHaveTextContent('视频帧生成完成，项目封面已自动更新');
   });
 
   it('hides frame generation while editing a project name', async () => {

src/components/ProjectLibrary.tsx

@@ -96,6 +96,18 @@ export function ProjectLibrary({ onProjectSelect }: ProjectLibraryProps) {
     }
   };
 
+  const refreshProjects = async () => {
+    const data = await getProjects();
+    setProjects(data);
+    if (currentProject?.id) {
+      const refreshedCurrentProject = data.find((project) => project.id === currentProject.id);
+      if (refreshedCurrentProject) {
+        setCurrentProject(refreshedCurrentProject);
+      }
+    }
+    return data;
+  };
+
   const ImportProgressPanel = () => {
     if (!importProgress) return null;
     const percent = typeof importProgress.percent === 'number'
@@ -378,14 +390,75 @@ export function ProjectLibrary({ onProjectSelect }: ProjectLibraryProps) {
 
   const handleGenerateFrames = async () => {
     if (!frameProject?.id) return;
+    const targetProject = frameProject;
     setIsGeneratingFrames(true);
     try {
-      const task = await parseMedia(frameProject.id, { parseFps: frameParseFps });
+      const task = await parseMedia(targetProject.id, { parseFps: frameParseFps });
       showNotice(`生成帧任务已入队 #${task.id}\n帧率: ${frameParseFps} FPS\n可在 Dashboard 查看进度。`, 'success');
-      const data = await getProjects();
-      setProjects(data);
+      await refreshProjects();
       setShowFrameConfig(false);
       setFrameProject(null);
+      if (task.id) {
+        setImportProgress({
+          kind: 'video',
+          phase: 'parsing',
+          title: '正在生成视频帧',
+          detail: task.message || `项目：${targetProject.name}`,
+          percent: task.progress ?? 0,
+        });
+        void waitForTaskDone(task.id, (progress) => {
+          setImportProgress({
+            kind: 'video',
+            phase: 'parsing',
+            title: '正在生成视频帧',
+            detail: progress.message || `任务状态: ${progress.status || 'running'}`,
+            percent: progress.progress,
+          });
+        }).then(async (completed) => {
+          if (completed.status === 'failed') {
+            setImportProgress({
+              kind: 'video',
+              phase: 'error',
+              title: '视频帧生成失败',
+              detail: completed.error || completed.message || targetProject.name,
+              percent: 100,
+            });
+            showNotice('视频帧生成失败，请检查后端服务或任务日志', 'error');
+            return;
+          }
+          if (completed.status === 'cancelled') {
+            setImportProgress({
+              kind: 'video',
+              phase: 'error',
+              title: '视频帧生成已取消',
+              detail: targetProject.name,
+              percent: 100,
+            });
+            showNotice('视频帧生成任务已取消', 'error');
+            return;
+          }
+          await refreshProjects();
+          setImportProgress({
+            kind: 'video',
+            phase: 'done',
+            title: '视频帧生成完成',
+            detail: '项目封面已自动更新',
+            percent: 100,
+          });
+          showNotice('视频帧生成完成，项目封面已自动更新', 'success');
+          scheduleProgressDismiss();
+        }).catch((err) => {
+          console.error('Frame generation polling failed:', err);
+          setImportProgress({
+            kind: 'video',
+            phase: 'error',
+            title: '视频帧生成进度同步失败',
+            detail: targetProject.name,
+            percent: 100,
+          });
+          showNotice('视频帧生成进度同步失败，请刷新项目库重试', 'error');
+        });
+      }
     } catch (err) {
       console.error('Frame generation failed:', err);
       showNotice('生成帧失败，请检查后端服务或项目源文件', 'error');