优化访问路径，使用index.html作为默认页面

- 将 linear-workflow.html 重命名为 index.html
- 更新所有配置文件和文档中的引用
- 现在可以直接访问 http://127.0.0.1:5175/
- 添加端口占用检查和自动处理功能
- 简化用户访问体验

package.json

@@ -2,9 +2,9 @@
   "name": "ai-agent-workflow",
   "version": "1.0.0",
   "description": "AI Agent 设计工作流 - 奶茶快闪店宝可梦主题设计",
-  "main": "linear-workflow.html",
+  "main": "index.html",
   "scripts": {
-    "dev": "npx http-server . -p 5175 -a 127.0.0.1 -o linear-workflow.html",
+    "dev": "npx http-server . -p 5175 -a 127.0.0.1 -o",
     "serve": "npx http-server . -p 5175 -a 127.0.0.1"
   },
   "keywords": [