feat: AI测试输出渲染Markdown/流式响应、Coze/Dify适配器优化

- 新增 MarkdownPreview 组件，支持 AI 测试输出 Markdown 渲染
- Coze 适配器优化：支持流式响应、工作流接口调用、SSE事件处理
- Dify 适配器优化：支持停止接口、流式聊天、SSE事件解析
- web-admin 添加 markdown-it 和 highlight.js 依赖
- AI 配置列表页面优化测试对话框输出显示

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

web-admin/package.json

@@ -16,12 +16,14 @@
     "dayjs": "^1.11.10",
     "echarts": "^5.4.3",
     "element-plus": "^2.4.4",
+    "markdown-it": "^14.1.1",
     "pinia": "^2.1.7",
     "vue": "^3.4.0",
     "vue-echarts": "^6.6.1",
     "vue-router": "^4.2.5"
   },
   "devDependencies": {
+    "@types/markdown-it": "^14.1.2",
     "@types/node": "^20.10.5",
     "@typescript-eslint/eslint-plugin": "^6.15.0",
     "@typescript-eslint/parser": "^6.15.0",