feat(app): 移除内置agents并添加CORS支持和技能上传优化

移除了agents/registry.json中的所有内置agents配置，将agents数组清空。
为web应用添加了CORS中间件支持，允许指定的前端地址跨域访问。
重构了技能上传功能，增加了LLM重写机制，自动规范化上传的技能格式。
新增了工具名称提取逻辑，从技能正文中自动识别Required Tools段落。
更新了技能学习候选者和草稿的载荷结构，添加评估报告统计信息。
修改了意图路由技能的说明，改进任务状态管理逻辑。

docs/product-discovery/beaver/README.md

@@ -8,7 +8,7 @@ Beaver is an enterprise Agent sandbox and execution platform. It combines privat
 
 - [Business Strategy HTML](./index.html): business-style product discovery, strategy canvas, target users, segmentation, and competitors.
 - [Product PRD HTML](./product-prd.html): product PRD, outcome roadmap, module job stories, WWA backlog items, and test scenarios.
-- [Product Discovery Report](./product-discovery-report.md): product understanding, users, JTBD, opportunities, assumptions, experiments, priorities, metrics, and 30/90 day recommendations.
+- [Product Discovery Report](./product-discovery-report.md): product understanding, users, JTBD, opportunities, assumptions, experiments, priorities, and 30/90 day recommendations.
 - [Product Architecture Brief](./product-architecture-brief.md): product-facing architecture across auth, deployment control, routing, app instances, frontend, backend, Agent runtime, tools, skills, memory, files, connectors, and operations.
 - [PRD](./PRD-beaver-agent-sandbox.md): full-product PRD for the Beaver Agent Sandbox.
 - [Validation Plan](./validation-plan.md): customer, product, technical, security, usability, and business validation plan.