feat: 实现 version/serve 骨架、迁移占位与健康检查

cmd/nixmsg/main.go

@@ -0,0 +1,25 @@
+package main
+
+import (
+	"fmt"
+	"os"
+)
+
+func main() {
+	if len(os.Args) < 2 {
+		fmt.Fprintln(os.Stderr, "usage: nixmsg <command>")
+		os.Exit(2)
+	}
+	switch os.Args[1] {
+	case "version":
+		cmdVersion(os.Args[2:])
+	case "serve":
+		if err := cmdServe(os.Args[2:]); err != nil {
+			fmt.Fprintln(os.Stderr, err)
+			os.Exit(1)
+		}
+	default:
+		fmt.Fprintf(os.Stderr, "unknown command: %s\n", os.Args[1])
+		os.Exit(2)
+	}
+}