fix: natural follow-up conversation flow

- Grader: separate followup hint from scoring feedback
- Interviewer: use followup hint directly without prefix/suffix
- Restored standard and choice question presentation paths

server/src/assessment/graph/nodes/grader.node.ts

@@ -252,10 +252,15 @@ Format your response as JSON:
       shouldFollowUp = false;
     }
 
+    let followupHintMsg: AIMessage | null = null;
     if (shouldFollowUp && followupHints.length > 0) {
       const hint = followupHints[Math.min(currentFollowUpCount, followupHints.length - 1)];
-      const hintLabel = isZh ? '追问方向' : isJa ? '追加の方向性' : 'Follow-up hint';
-      enhancedFeedback = `${result.feedback}\n\n${hintLabel}: ${hint}`;
+      const hintLabel = isZh
+        ? `让我帮你完善一下：${hint}`
+        : isJa
+          ? `もう少し詳しく伺います：${hint}`
+          : `Let me help you elaborate: ${hint}`;
+      followupHintMsg = new AIMessage(hintLabel);
     }
 
     const feedbackMessage = new AIMessage(
@@ -271,8 +276,12 @@ Format your response as JSON:
       saysIDontKnow,
     });
 
+    const feedbackHistoryMessages = followupHintMsg
+      ? [feedbackMessage, followupHintMsg]
+      : [feedbackMessage];
+
     return {
-      feedbackHistory: [feedbackMessage],
+      feedbackHistory: feedbackHistoryMessages,
       scores: newScores,
       shouldFollowUp: shouldFollowUp,
       followUpCount: shouldFollowUp ? currentFollowUpCount + 1 : 0,

server/src/assessment/graph/nodes/interviewer.node.spec.ts

@@ -81,14 +81,13 @@ describe('interviewerNode', () => {
   });
 
   describe('follow-up mode', () => {
-    it('should include feedback in follow-up prompt', async () => {
+    it('should use last feedbackHistory message content as follow-up prompt', async () => {
       const state = baseState({
         shouldFollowUp: true,
-        feedbackHistory: [new AIMessage('Feedback: You need more details')],
+        feedbackHistory: [new AIMessage('You need more details')],
       });
       const result = await interviewerNode(state);
       const msg = (result.messages as any)[0].content as string;
-      expect(msg).toContain('Follow-up');
       expect(msg).toContain('You need more details');
     });
 

server/src/assessment/graph/nodes/interviewer.node.ts

@@ -49,27 +49,7 @@ export const interviewerNode = async (
   ) {
     const lastFeedbackMsg =
       state.feedbackHistory[state.feedbackHistory.length - 1];
-    const feedbackText = lastFeedbackMsg.content.toString();
-
-    const feedbackMatch = feedbackText.match(
-      /(?:Feedback|反馈|フィードバック): ([\s\S]*)/i,
-    );
-    const specificFeedback = feedbackMatch
-      ? feedbackMatch[1].trim()
-      : feedbackText;
-
-    const followUpLabel = isZh
-      ? '补充追问'
-      : isJa
-        ? '追加の質問'
-        : 'Follow-up Clarification';
-    const followUpInstruction = isZh
-      ? '根据以上反馈，请补充更具体的信息：'
-      : isJa
-        ? '上記のフィードバックに基づき、より具体的な情報を追加してください：'
-        : 'Based on the feedback above, please provide more specific details:';
-
-    prompt = `${followUpLabel}\n\n${specificFeedback}\n\n${followUpInstruction}`;
+    prompt = lastFeedbackMsg.content.toString();
   } else if (currentQuestion.questionType === 'MULTIPLE_CHOICE' && currentQuestion.options?.length > 0) {
     const label = isZh
       ? `问题 ${currentQuestionIndex + 1}`