feat(mcp): add Model Context Protocol integration

Implement comprehensive MCP support with stdio/HTTP/SSE transports, environment variable configuration (env and envFile), custom headers, tool registration, and automatic resource cleanup. Includes full test coverage and VSCode-compatible configuration.

- Added pkg/mcp/manager.go for server lifecycle management
- Added pkg/tools/mcp_tool.go for tool wrapping
- Integrated into agent loop with cleanup
- Support for envFile loading (.env format)
- Headers injection for HTTP/SSE authentication
- Example configs for filesystem, github, brave-search, postgres

go.mod

@@ -11,6 +11,7 @@ require (
 	github.com/google/uuid v1.6.0
 	github.com/gorilla/websocket v1.5.3
 	github.com/larksuite/oapi-sdk-go/v3 v3.5.3
+	github.com/modelcontextprotocol/go-sdk v1.3.0
 	github.com/mymmrac/telego v1.6.0
 	github.com/open-dingtalk/dingtalk-stream-sdk-go v0.9.1
 	github.com/openai/openai-go/v3 v3.22.0
@@ -19,7 +20,7 @@ require (
 	golang.org/x/oauth2 v0.35.0
 )
 
-
+require github.com/yosida95/uritemplate/v3 v3.0.2 // indirect
 
 require (
 	github.com/andybalholm/brotli v1.2.0 // indirect
@@ -28,9 +29,9 @@ require (
 	github.com/bytedance/sonic/loader v0.5.0 // indirect
 	github.com/cloudwego/base64x v0.1.6 // indirect
 	github.com/github/copilot-sdk/go v0.1.23
-	github.com/google/jsonschema-go v0.4.2 // indirect
 	github.com/go-resty/resty/v2 v2.17.1 // indirect
 	github.com/gogo/protobuf v1.3.2 // indirect
+	github.com/google/jsonschema-go v0.4.2 // indirect
 	github.com/grbit/go-json v0.11.0 // indirect
 	github.com/klauspost/compress v1.18.4 // indirect
 	github.com/klauspost/cpuid/v2 v2.3.0 // indirect
@@ -47,5 +48,4 @@ require (
 	golang.org/x/net v0.50.0 // indirect
 	golang.org/x/sync v0.19.0 // indirect
 	golang.org/x/sys v0.41.0 // indirect
-
 )