feat(gui): carry the question detail field over the wire and render it

AskUserQuestionItem.detail is part of the user-interaction seam contract
but the web frame schema dropped it and the composer never rendered it
(review r3635427108). askUserQuestionItemSchema now forwards detail, the
composer renders it under the title in the description text style, and
the fixture's multi-select question carries one.

packages/client/ui-question/src/client/QuestionComposer.module.css

@@ -59,6 +59,14 @@
   white-space: nowrap;
 }
 
+.detail {
+  margin: 2px 0 0;
+  color: var(--dsw-alias-label-tertiary);
+  font-size: 13px;
+  line-height: 20px;
+  font-weight: 400;
+}
+
 .headerActions,
 .footerActions {
   display: flex;

packages/client/ui-question/src/client/QuestionComposer.tsx

@@ -171,6 +171,7 @@ function QuestionFlow({ pending }: { pending: PendingQuestion }) {
                 : question.question}</span>
               {question.multiSelect === true && <span className={css.multiSelectHint}>可多选</span>}
             </h2>
+            {question.detail !== undefined && <p className={css.detail}>{question.detail}</p>}
           </div>
           <div className={css.headerActions}>
             <span className={css.progress}>{index + 1} / {questions.length}</span>

packages/client/ui-question/tests/question-composer.spec.tsx

@@ -27,6 +27,7 @@ const kit = {
 const QUESTIONS = [
   {
     id: 'profile', header: '偏好', question: '选择候选人类型',
+    detail: '按当前空缺岗位的优先级选择。',
     options: [
       { label: '工程落地型 (Recommended)', description: '优先工程交付。' },
       { label: '研究潜力型', description: '优先研究能力。' },
@@ -64,11 +65,14 @@ describe('QuestionComposer', () => {
     expect(screen.getByText('1 / 3')).toBeTruthy()
     expect(screen.getByText('推荐')).toBeTruthy()
     expect(screen.getByText('工程落地型')).toBeTruthy()
+    expect(screen.getByText('按当前空缺岗位的优先级选择。')).toBeTruthy()
     fireEvent.keyDown(screen.getByRole('radio', { name: /工程落地型/ }), { key: 'Enter' })
     expect(respond).not.toHaveBeenCalled()
     fireEvent.click(screen.getByRole('radio', { name: /工程落地型/ }))
 
     expect(screen.getByText('2 / 3')).toBeTruthy()
+    // detail is per-question: the second question carries none.
+    expect(screen.queryByText('按当前空缺岗位的优先级选择。')).toBeNull()
     expect(screen.queryByRole('button', { name: '填写答案' })).toBeNull()
     const custom = screen.getByPlaceholderText('输入你的答案')
     fireEvent.change(custom, { target: { value: '要能独立排查线上问题' } })