fix: preserve video extensions on AI design downloads

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

@@ -427,6 +427,79 @@ describe('AI design Main route boundary', () => {
     await expect(readFile(savedPath, 'utf8')).resolves.toBe('image-bytes');
   });
 
+  it.each([
+    ['mp4', 'video/mp4'],
+    ['mov', 'video/quicktime'],
+    ['webm', 'video/webm'],
+  ])('streams a private %s asset into a video save location', async (extension, mimeType) => {
+    temporaryDirectory = await mkdtemp(join(tmpdir(), 'makelore-design-download-'));
+    const savedPath = join(temporaryDirectory, `animation.${extension}`);
+    electronMocks.showSaveDialog.mockResolvedValue({ canceled: false, filePath: savedPath });
+    const expectedBytes = `video-${extension}-bytes`;
+    const content = new Response(expectedBytes, {
+      status: 200,
+      headers: { 'Content-Type': mimeType },
+    });
+    const getContentType = vi.spyOn(content.headers, 'get');
+    const openAssetContent = vi.fn().mockResolvedValue(content);
+    const response = createResponse();
+
+    await handleImageWorkspaceRoutes(
+      createRequest('POST', { defaultFileName: `Ocean animation.${extension}` }),
+      response.res,
+      new URL(
+        'http://127.0.0.1/api/works/image-workspace/workspaces/workspace-one/assets/asset-one/download',
+      ),
+      { imageWorkspace: { openAssetContent } } as unknown as HostApiContext,
+    );
+
+    expect(electronMocks.showSaveDialog).toHaveBeenCalledWith(expect.objectContaining({
+      defaultPath: expect.stringContaining(`Ocean animation.${extension}`),
+      filters: [
+        { name: '设计资产', extensions: [extension] },
+        { name: '所有文件', extensions: ['*'] },
+      ],
+    }));
+    expect(getContentType).toHaveBeenCalledWith('content-type');
+    expect(content.headers.get('content-type')).toBe(mimeType);
+    expect(openAssetContent).toHaveBeenCalledWith('workspace-one', 'asset-one');
+    expect(response.json()).toMatchObject({
+      success: true,
+      data: { status: 'saved' },
+    });
+    await expect(readFile(savedPath, 'utf8')).resolves.toBe(expectedBytes);
+  });
+
+  it('rejects a private download response that is not an image or video', async () => {
+    temporaryDirectory = await mkdtemp(join(tmpdir(), 'makelore-design-download-'));
+    const savedPath = join(temporaryDirectory, 'payload.mp4');
+    electronMocks.showSaveDialog.mockResolvedValue({ canceled: false, filePath: savedPath });
+    const response = createResponse();
+
+    await handleImageWorkspaceRoutes(
+      createRequest('POST', { defaultFileName: 'payload.mp4' }),
+      response.res,
+      new URL(
+        'http://127.0.0.1/api/works/image-workspace/workspaces/workspace-one/assets/asset-one/download',
+      ),
+      {
+        imageWorkspace: {
+          openAssetContent: vi.fn().mockResolvedValue(new Response('untrusted', {
+            status: 200,
+            headers: { 'Content-Type': 'application/octet-stream' },
+          })),
+        },
+      } as unknown as HostApiContext,
+    );
+
+    expect(response.json()).toMatchObject({
+      success: false,
+      code: 'DESIGN_ASSET_DOWNLOAD_FAILED',
+      error: '生成资产暂时无法下载，请稍后重试',
+    });
+    await expect(readFile(savedPath)).rejects.toMatchObject({ code: 'ENOENT' });
+  });
+
   it('preserves an existing destination when the private image stream fails', async () => {
     temporaryDirectory = await mkdtemp(join(tmpdir(), 'makelore-design-download-'));
     const savedPath = join(temporaryDirectory, 'existing.png');