feat: mock配置迁移至JSON格式并修复body匹配

- 将mock配置从YAML格式迁移到JSON格式
- 修复JSON字符串格式body匹配失败问题
- 添加MCP功能模块
- 更新mock-spec.md规范文档

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

mocks/v1/products/export.yaml

@@ -1,12 +0,0 @@
-name: "prod_export_pdf"
-request:
-  method: "GET"
-  path: "/v1/products/report"
-  body: '{"username":"user001","password":"password123"}'
-response:
-  status: 200
-  headers:
-    Content-Type: "application/pdf"
-    Content-Disposition: "attachment; filename=report.pdf"
-  # 智能协议：引擎会自动识别前缀并异步读取磁盘文件
-  body: "file://./storage/v1/hello.pdf"

mocks/v1/products/export_pdf.json

@@ -0,0 +1,16 @@
+{
+  "name": "prod_export_pdf",
+  "request": {
+    "method": "GET",
+    "path": "/v1/products/report",
+    "body": "{\"username\":\"user001\",\"password\":\"password123\"}"
+  },
+  "response": {
+    "status": 200,
+    "headers": {
+      "Content-Type": "application/pdf",
+      "Content-Disposition": "attachment; filename=report.pdf"
+    },
+    "body": "file://./storage/v1/hello.pdf"
+  }
+}