feat: añadir cliente MCP para consumir servidores externos

Implementa el cliente MCP que permite a los agentes conectarse a servidores
MCP externos y usar sus tools como si fueran tools nativas del agente.

Arquitectura implementada:
- shell/mcp/client.go: Cliente MCP con soporte stdio y SSE
- shell/mcp/manager.go: Gestor de múltiples clientes MCP
- tools/mcptools/mcp.go: Bridge que convierte MCP tools → tools.Tool
- shell/mcp/server.go: Movido desde shell/protocols/ para colocación junto al client

Cambios en config:
- MCPServerCfg extendido con campos Transport, Command, Args, Env, Headers,
  Prefix, Timeout para soportar stdio y SSE transport

Integración en runtime:
- agents/runtime.go: Inicializa MCP manager si config.Tools.MCP.Enabled
- buildToolRegistry: Registra tools MCP automáticamente con prefijos configurables
- Agent: Campo mcpManager que se cierra en shutdown

Transportes soportados:
- stdio: Lanza subproceso (ej: npx -y @anthropic/mcp-server-brave-search)
- SSE: Se conecta a servidor HTTP MCP

Las tools MCP son indistinguibles de tools nativas desde el punto de vista
del LLM. Auto-discovery via ListTools(), conversión de JSON Schema a tools.Param.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

agents/runtime.go

@@ -29,6 +29,7 @@ import (
 	shellknowledge "github.com/enmanuel/agents/shell/knowledge"
 	shelllm "github.com/enmanuel/agents/shell/llm"
 	"github.com/enmanuel/agents/shell/matrix"
+	shellmcp "github.com/enmanuel/agents/shell/mcp"
 	shellmem "github.com/enmanuel/agents/shell/memory"
 	"github.com/enmanuel/agents/shell/ssh"
 	"github.com/enmanuel/agents/tools"
@@ -37,6 +38,7 @@ import (
 	toolhttp "github.com/enmanuel/agents/tools/http"
 	toolknowledge "github.com/enmanuel/agents/tools/knowledgetools"
 	toolmatrix "github.com/enmanuel/agents/tools/matrix"
+	toolmcp "github.com/enmanuel/agents/tools/mcptools"
 	toolmemory "github.com/enmanuel/agents/tools/memorytools"
 	toolssh "github.com/enmanuel/agents/tools/ssh"
 	toolweather "github.com/enmanuel/agents/tools/weather"
@@ -62,6 +64,7 @@ type Agent struct {
 	toolReg     *tools.Registry
 	logger      *slog.Logger
 	cryptoStore io.Closer // non-nil when E2EE is enabled; closed on shutdown
+	mcpManager  *shellmcp.Manager // nil when MCP client is disabled
 
 	// Lifecycle — cancel stops this agent individually; done is closed when Run returns.
 	cancel context.CancelFunc
@@ -236,8 +239,20 @@ func New(cfg *config.AgentConfig, rules []decision.Rule, agentACL acl.ACL, logge
 		logger.Info("acl enabled (centralized security policy)")
 	}
 
+	// MCP client manager — connects to external MCP servers
+	var mcpManager *shellmcp.Manager
+	if cfg.Tools.MCP.Enabled && len(cfg.Tools.MCP.Servers) > 0 {
+		var mcpErr error
+		mcpManager, mcpErr = shellmcp.NewManager(context.Background(), cfg.Tools.MCP.Servers, logger)
+		if mcpErr != nil {
+			logger.Error("mcp_manager_init_failed", "err", mcpErr)
+		} else {
+			logger.Info("mcp manager initialized", "servers", len(cfg.Tools.MCP.Servers))
+		}
+	}
+
 	// Tool registry — register tools enabled in config
-	toolReg := buildToolRegistry(cfg, sshExec, matrixClient, memStore, kStore, roomCtx, logger)
+	toolReg := buildToolRegistry(cfg, sshExec, matrixClient, memStore, kStore, mcpManager, roomCtx, logger)
 
 	// Rate limiting for tools
 	if cfg.Security.ToolRateLimit.Enabled {
@@ -272,7 +287,8 @@ func New(cfg *config.AgentConfig, rules []decision.Rule, agentACL acl.ACL, logge
 		toolReg:     toolReg,
 		logger:      logger,
 		cryptoStore: cryptoStore,
-		done:           make(chan struct{}),
+		mcpManager:  mcpManager,
+		done:        make(chan struct{}),
 		commands:       make(map[string]CommandHandler),
 		cmdAliases:     command.BuiltinNames(),
 		startTime:      time.Now(),
@@ -401,6 +417,9 @@ func (a *Agent) Run(ctx context.Context) error {
 	if a.knowledgeStore != nil {
 		defer a.knowledgeStore.Close()
 	}
+	if a.mcpManager != nil {
+		defer a.mcpManager.Close()
+	}
 	a.logger.Info("agent starting",
 		"id", a.cfg.Agent.ID,
 		"name", a.cfg.Agent.Name,
@@ -980,6 +999,7 @@ func buildToolRegistry(
 	matrixClient *matrix.Client,
 	memStore memory.Store,
 	kStore *shellknowledge.FileStore,
+	mcpManager *shellmcp.Manager,
 	roomCtx *toolmemory.RoomContext,
 	logger *slog.Logger,
 ) *tools.Registry {
@@ -1031,5 +1051,30 @@ func buildToolRegistry(
 		logger.Debug("registered knowledge tools")
 	}
 
+	// MCP tools — register tools from all connected MCP servers
+	if mcpManager != nil {
+		for serverName, mcpClient := range mcpManager.AllClients() {
+			// Find the config for this server to get prefix, filter, timeout
+			var serverCfg *config.MCPServerCfg
+			for i := range cfg.Tools.MCP.Servers {
+				if cfg.Tools.MCP.Servers[i].Name == serverName {
+					serverCfg = &cfg.Tools.MCP.Servers[i]
+					break
+				}
+			}
+			if serverCfg == nil {
+				logger.Warn("no config found for MCP server", "name", serverName)
+				continue
+			}
+
+			// Convert and register MCP tools
+			mcpTools := toolmcp.FromMCPServer(mcpClient, serverCfg.Prefix, serverCfg.Tools, serverCfg.Timeout, logger)
+			for _, tool := range mcpTools {
+				reg.Register(tool)
+			}
+			logger.Debug("registered MCP tools", "server", serverName, "count", len(mcpTools))
+		}
+	}
+
 	return reg
 }