feat(agent): 实现委派工具重构，支持子代理和代理团队模式

- 新增 spawn_subagent 和 spawn_agent_team 工具，替代原有的 spawn 工具
- 重构 DelegationManager 以支持单个子代理和代理团队两种委派模式
- 更新系统提示词中的委派策略说明，明确使用场景和区别
- 添加技能上下文传递功能，确保委派任务遵循指定技能
- 实现代理内部的受控下游委派机制，防止无限嵌套
- 更新工具注册和上下文设置逻辑以适配新架构

app-instance/backend/nanobot/skills/outlook/SKILL.md

@@ -17,7 +17,7 @@ Only use this skill if Outlook MCP tools are available in the current tool list,
 ## V1 routing rules
 
 - Keep Outlook execution in the main agent turn.
-- Do not `spawn` a local subagent for Outlook work in V1, because the local delegated agent does not inherit MCP tools.
+- Do not use `spawn_subagent` for Outlook work in V1, because the local delegated agent does not inherit MCP tools.
 - Do not use the built-in `email` channel for Outlook mailbox operations. Outlook actions should go through MCP -> Outlook MCP server -> Microsoft Graph.
 
 ## Tool usage rules