feat(teacher): show a subtle hint action in the empty composer

tests/e2e/teacher-reply-layout.spec.ts

@@ -22,6 +22,44 @@ test.beforeAll(async () => {
 });
 test.afterAll(async () => { await server?.close(); });
 for (const width of [319, 508]) {
+  test(`empty-composer hint stays lightweight and keeps the send position stable at ${width}px`, async ({ page }) => {
+    await page.setViewportSize({ width: 1180, height: 800 });
+    await page.goto(`${url}?kind=ordinary&width=${width}`);
+    const input = page.getByRole('textbox', { name: '向智能体提问' });
+    const hint = page.getByRole('button', { name: '给我一点提示', exact: true });
+    const send = page.getByRole('button', { name: '提问', exact: true });
+    const sent = () => page.evaluate(() => (window as unknown as { __teacherReplyInputs: unknown[] }).__teacherReplyInputs);
+    await expect(hint).toBeEnabled();
+    await expect(hint).toHaveCSS('background-color', 'rgba(0, 0, 0, 0)');
+    const initialSend = (await send.boundingBox())!;
+    const hintBounds = (await hint.boundingBox())!;
+    expect(hintBounds.x).toBeLessThan(initialSend.x);
+    expect(await sent()).toEqual([]);
+    await input.fill('我想先自己说说');
+    await expect(hint).toHaveCount(0);
+    expect(await send.boundingBox()).toEqual(initialSend);
+    await input.fill('   ');
+    await expect(hint).toBeVisible();
+    await input.fill('');
+    await expect(hint).toBeVisible();
+    expect(await send.boundingBox()).toEqual(initialSend);
+    expect(await sent()).toEqual([]);
+    await hint.click();
+    await expect(page.getByText('我们可以先从一个小地方开始。')).toBeVisible();
+    expect(await sent()).toEqual([{ requestId: expect.any(String), text: '给我一点提示', intent: 'suggestions', references: [], sourceConversationId: 'source' }]);
+    await expect(page.getByRole('button', { name: '我也说不清，你带我看看', exact: true })).toHaveCount(0);
+    await expect(page.locator('.consultation-messages').getByRole('button', { name: '给我一点提示', exact: true })).toHaveCount(0);
+    const card = page.getByRole('button', { name: '可以从哪个小地方开始？' });
+    await expect(card).toBeVisible();
+    await input.fill('留着我自己的草稿');
+    await expect(hint).toHaveCount(0);
+    await card.click();
+    await expect(page.getByText('好，我们就从这一个问题聊起。')).toBeVisible();
+    await expect(input).toHaveValue('留着我自己的草稿');
+    expect(await sent()).toHaveLength(2);
+    await page.screenshot({ path: test.info().outputPath(`composer-hint-${width}.png`) });
+  });
+
   test(`rich replies keep code, tables and images inside the panel at ${width}px`, async ({ page }) => {
     await page.setViewportSize({ width: 1180, height: 800 });
     const errors: string[] = [];