Add MCP integration with MCPServer for tool-based interactions

- Introduce `MCPServer` to support connecting to MCP servers via stdio, SSE, or HTTP.
- Implement tool fetching, management, and invocation through MCP.
- Add `WithMCPServer` method to `ToolBox` for seamless tool integration.
- Extend schema package to handle raw JSON schemas for MCP tools.
- Update documentation with MCP usage guidelines and examples.

go.mod

@@ -8,7 +8,9 @@ require (
 	github.com/charmbracelet/bubbles v0.21.0
 	github.com/charmbracelet/bubbletea v1.3.10
 	github.com/charmbracelet/lipgloss v1.1.0
+	github.com/joho/godotenv v1.5.1
 	github.com/liushuangls/go-anthropic/v2 v2.17.0
+	github.com/modelcontextprotocol/go-sdk v1.2.0
 	github.com/openai/openai-go v1.12.0
 	golang.org/x/image v0.35.0
 	google.golang.org/genai v1.43.0
@@ -30,11 +32,11 @@ require (
 	github.com/go-logr/logr v1.4.3 // indirect
 	github.com/go-logr/stdr v1.2.2 // indirect
 	github.com/google/go-cmp v0.7.0 // indirect
+	github.com/google/jsonschema-go v0.3.0 // indirect
 	github.com/google/s2a-go v0.1.9 // indirect
 	github.com/googleapis/enterprise-certificate-proxy v0.3.11 // indirect
 	github.com/googleapis/gax-go/v2 v2.16.0 // indirect
 	github.com/gorilla/websocket v1.5.3 // indirect
-	github.com/joho/godotenv v1.5.1 // indirect
 	github.com/lucasb-eyer/go-colorful v1.2.0 // indirect
 	github.com/mattn/go-isatty v0.0.20 // indirect
 	github.com/mattn/go-localereader v0.0.1 // indirect
@@ -48,6 +50,7 @@ require (
 	github.com/tidwall/pretty v1.2.1 // indirect
 	github.com/tidwall/sjson v1.2.5 // indirect
 	github.com/xo/terminfo v0.0.0-20220910002029-abceb7e1c41e // indirect
+	github.com/yosida95/uritemplate/v3 v3.0.2 // indirect
 	go.opentelemetry.io/auto/sdk v1.2.1 // indirect
 	go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp v0.64.0 // indirect
 	go.opentelemetry.io/otel v1.39.0 // indirect
@@ -55,6 +58,7 @@ require (
 	go.opentelemetry.io/otel/trace v1.39.0 // indirect
 	golang.org/x/crypto v0.47.0 // indirect
 	golang.org/x/net v0.49.0 // indirect
+	golang.org/x/oauth2 v0.32.0 // indirect
 	golang.org/x/sys v0.40.0 // indirect
 	golang.org/x/text v0.33.0 // indirect
 	google.golang.org/genproto/googleapis/rpc v0.0.0-20260122232226-8e98ce8d340d // indirect