feat: add ServiceRuntime to MCP Service + use s.Core()

MCP Service now embeds *core.ServiceRuntime[McpOptions] like all v0.8.0
services. OnStartup uses s.Core() instead of casting coreRef.

Co-Authored-By: Virgil <virgil@lethean.io>

pkg/mcp/mcp.go

@@ -14,6 +14,7 @@ import (
 	"strings"
 	"sync"
 
+	core "dappco.re/go/core"
 	"forge.lthn.ai/core/go-io"
 	"forge.lthn.ai/core/go-log"
 	"forge.lthn.ai/core/go-process"
@@ -27,6 +28,8 @@ import (
 //	svc, err := mcp.New(mcp.Options{WorkspaceRoot: "/home/user/project"})
 //	defer svc.Shutdown(ctx)
 type Service struct {
+	*core.ServiceRuntime[McpOptions] // Core access via s.Core()
+
 	server         *mcp.Server
 	workspaceRoot  string           // Root directory for file operations (empty = unrestricted)
 	medium         io.Medium        // Filesystem medium for sandboxed operations
@@ -39,9 +42,12 @@ type Service struct {
 	wsMu           sync.Mutex       // Protects wsServer and wsAddr
 	stdioMode      bool             // True when running via stdio transport
 	tools          []ToolRecord     // Parallel tool registry for REST bridge
-	coreRef        any              // *core.Core — stored by Register, used by OnStartup
+	coreRef        any              // Deprecated: use s.Core() via ServiceRuntime
 }
 
+// McpOptions configures the MCP service runtime.
+type McpOptions struct{}
+
 // Options configures a Service.
 //
 //	svc, err := mcp.New(mcp.Options{

pkg/mcp/register.go

@@ -39,15 +39,19 @@ func Register(c *core.Core) core.Result {
 		return core.Result{Value: err, OK: false}
 	}
 
-	svc.coreRef = c
+	svc.ServiceRuntime = core.NewServiceRuntime(c, McpOptions{})
+	svc.coreRef = c // kept until all methods migrate to s.Core()
 
 	return core.Result{Value: svc, OK: true}
 }
 
 // OnStartup implements core.Startable — registers MCP transport commands.
+//
+//	core-agent mcp    — start MCP server on stdio
+//	core-agent serve  — start MCP server on HTTP
 func (s *Service) OnStartup(ctx context.Context) core.Result {
-	c, ok := s.coreRef.(*core.Core)
-	if !ok || c == nil {
+	c := s.Core()
+	if c == nil {
 		return core.Result{OK: true}
 	}