fix(canvas): cap video duration choices

tests/unit/image-canvas-page.test.tsx

@@ -510,6 +510,69 @@ describe('ImageCanvas Workspace-first design experience', () => {
     expect(screen.getByRole('button', { name: '确认并开始生成' })).toBeEnabled();
   });
 
+  it('limits legacy video durations to 2-6 seconds and preserves 6 seconds through confirmation', async () => {
+    const videoConversation = conversationFixture();
+    const videoQuote = videoConversation.messages[1].generationQuote!;
+    videoConversation.brief.medium = 'video';
+    videoQuote.medium = 'video';
+    videoQuote.generationParameters = {
+      ...videoQuote.generationParameters,
+      durationSeconds: 10,
+    };
+    videoQuote.generationOptions.durations = [2, 6, 7, 15].map((value) => ({
+      value,
+      label: `${value} 秒`,
+      default: value === 10,
+      disabled: false,
+      multiplier: 1,
+    }));
+    fetchImageWorkspaceConversationMock.mockResolvedValueOnce(videoConversation);
+    updateImageWorkspaceGenerationQuoteMock.mockImplementationOnce(async (
+      _workspaceId: string,
+      _quoteId: string,
+      finalPrompt: string,
+      generationParameters: DesignGenerationQuote['generationParameters'],
+    ) => ({
+      ...videoQuote,
+      finalPrompt,
+      generationParameters,
+    }));
+
+    render(<MemoryRouter><ImageCanvas /></MemoryRouter>);
+
+    const durationSelect = await screen.findByTestId('design-quote-duration');
+    expect(durationSelect).toHaveValue('');
+    expect(within(durationSelect).getAllByRole('option').map((option) => option.getAttribute('value')))
+      .toEqual(['', '2', '6']);
+
+    fireEvent.change(durationSelect, { target: { value: '6' } });
+
+    await waitFor(() => expect(updateImageWorkspaceGenerationQuoteMock).toHaveBeenCalledWith(
+      'workspace-cloud',
+      'quote-one',
+      videoQuote.finalPrompt,
+      {
+        ...videoQuote.generationParameters,
+        durationSeconds: 6,
+      },
+    ));
+    await waitFor(() => expect(screen.getByTestId('design-quote-duration')).toHaveValue('6'));
+    fireEvent.click(screen.getByRole('button', { name: '确认并开始生成' }));
+
+    await waitFor(() => expect(confirmImageWorkspaceGenerationMock).toHaveBeenCalledWith(
+      'workspace-cloud',
+      'conversation-cloud',
+      1,
+      'quote-one',
+      expect.stringMatching(/^turn-/),
+      videoQuote.finalPrompt,
+      {
+        ...videoQuote.generationParameters,
+        durationSeconds: 6,
+      },
+    ));
+  });
+
   it('offers an actionable retry when re-quoting fails', async () => {
     updateImageWorkspaceGenerationQuoteMock.mockRejectedValueOnce(
       new ImageWorkspaceApiError(409, 'generation_quote_invalid', '当前生成方案已失效'),