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>

package.json

@@ -11,5 +11,8 @@
   },
   "devDependencies": {
     "concurrently": "^8.2.2"
+  },
+  "dependencies": {
+    "playwright": "^1.60.0"
   }
-}
+}