fix: shuffleArray bug + Playwright多轮对话测试 + 初学者考核脚本

- 修复 shuffleArray 返回新数组但调用处用 const 未接收返回值（3处）
- 新增 test-multiround.mjs Playwright 多轮对话测试（简答+追问全流程）
- 新增 do-assessment.mjs / check-result.mjs 考核体验脚本
- CLAUDE.md 增加 AI 工作流指令规则
- package.json 添加 playwright 依赖

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

server/src/assessment/services/question-bank.service.ts

@@ -541,8 +541,8 @@ export class QuestionBankService {
       for (const dw of dimensionWeights) {
         const dimName = dw.name as QuestionDimension;
         const targetForDim = Math.round(count * dw.weight / totalWeight);
-        const pool = availableItems.filter(i => i.dimension === dimName && !usedIds.has(i.id));
-        this.shuffleArray(pool);
+        let pool = availableItems.filter(i => i.dimension === dimName && !usedIds.has(i.id));
+        pool = this.shuffleArray(pool);
         const take = Math.min(targetForDim, pool.length);
         for (let i = 0; i < take; i++) {
           selected.push(pool[i]);
@@ -550,7 +550,7 @@ export class QuestionBankService {
         }
       }
       availableItems = availableItems.filter(i => !usedIds.has(i.id));
-      this.shuffleArray(availableItems);
+      availableItems = this.shuffleArray(availableItems);
       while (selected.length < count && availableItems.length > 0) {
         const item = availableItems.pop()!;
         selected.push(item);
@@ -572,7 +572,7 @@ export class QuestionBankService {
         if (dimIdx >= DIMENSIONS.length * 3) break;
       }
       if (selected.length < count && availableItems.length > 0) {
-        this.shuffleArray(availableItems);
+        availableItems = this.shuffleArray(availableItems);
         for (const item of availableItems) {
           if (selected.length >= count) break;
           if (!usedIds.has(item.id)) {