fix(canvas): soften design conversation

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

@@ -115,6 +115,10 @@ describe('AI Design Canvas page', () => {
     render(<ImageCanvas />);
 
     const conversation = screen.getByTestId('image-workspace-conversation');
+    expect(conversation).toHaveClass('bg-background');
+    expect(conversation).not.toHaveClass('bg-surface-subtle/45');
+    expect(within(conversation).getByTestId('design-message-composer')).toHaveClass('max-w-[50rem]');
+    expect(within(conversation).getByTestId('design-message-composer-surface')).toHaveClass('chat-composer-surface');
     expect(within(conversation).queryByRole('heading', { name: '和 AI 一起完善创作' })).not.toBeInTheDocument();
     expect(within(conversation).getByRole('heading', { name: '制作方案' })).toBeInTheDocument();
     expect(within(conversation).getByRole('textbox', { name: '创作提示词' })).toHaveValue(
@@ -317,7 +321,7 @@ describe('AI Design Canvas page', () => {
     render(<ImageCanvas />);
 
     const conversation = screen.getByTestId('image-workspace-conversation');
-    expect(within(conversation).getByRole('heading', { name: '先把脑中的画面说出来' })).toBeInTheDocument();
+    expect(within(conversation).getByRole('heading', { name: '你想让麦洛和你一起创作什么？' })).toBeInTheDocument();
     expect(within(conversation).queryByText('画面想要什么感觉？')).not.toBeInTheDocument();
     fireEvent.click(within(conversation).getByRole('button', { name: '我想做一张热闹的社团招新海报' }));
     expect(within(conversation).getByRole('textbox', { name: '告诉 AI 你想创作什么' })).toHaveValue(
@@ -381,7 +385,7 @@ describe('AI Design Canvas page', () => {
     fireEvent.change(screen.getByRole('textbox', { name: '告诉 AI 你想创作什么' }), {
       target: { value: '画一只会做饭的机器人' },
     });
-    fireEvent.click(screen.getByRole('button', { name: '发送消息' }));
+    fireEvent.click(screen.getByRole('button', { name: '发送' }));
 
     await waitFor(() => {
       expect(toastErrorMock).toHaveBeenCalledWith(