Add mcp-master binary and build target

New cmd/mcp-master/ entry point following the agent pattern:
cobra CLI with --config, version, and server commands.

Makefile: add mcp-master target, update all and clean targets.
Example config: deploy/examples/mcp-master.toml with all sections.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

cmd/mcp-master/main.go

@@ -0,0 +1,49 @@
+package main
+
+import (
+	"fmt"
+	"log"
+	"os"
+
+	"git.wntrmute.dev/mc/mcp/internal/config"
+	"git.wntrmute.dev/mc/mcp/internal/master"
+	"github.com/spf13/cobra"
+)
+
+var (
+	version = "dev"
+	cfgPath string
+)
+
+func main() {
+	root := &cobra.Command{
+		Use:   "mcp-master",
+		Short: "Metacircular Control Plane master",
+	}
+	root.PersistentFlags().StringVarP(&cfgPath, "config", "c", "", "config file path")
+
+	root.AddCommand(&cobra.Command{
+		Use:   "version",
+		Short: "Print version",
+		Run: func(cmd *cobra.Command, args []string) {
+			fmt.Println(version)
+		},
+	})
+
+	root.AddCommand(&cobra.Command{
+		Use:   "server",
+		Short: "Start the master server",
+		RunE: func(cmd *cobra.Command, args []string) error {
+			cfg, err := config.LoadMasterConfig(cfgPath)
+			if err != nil {
+				return fmt.Errorf("load config: %w", err)
+			}
+			return master.Run(cfg, version)
+		},
+	})
+
+	if err := root.Execute(); err != nil {
+		log.Fatal(err)
+		os.Exit(1)
+	}
+}