Add mcproxyctl CLI for gRPC admin API

Introduces a new command-line tool for managing mc-proxy via the gRPC
admin API over Unix socket. Commands include route and firewall rule
CRUD operations, health checks, and status queries.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

cmd/mcproxyctl/health.go

@@ -0,0 +1,38 @@
+package main
+
+import (
+	"context"
+	"fmt"
+	"time"
+
+	"github.com/spf13/cobra"
+
+	"git.wntrmute.dev/kyle/mc-proxy/client/mcproxy"
+)
+
+func healthCmd() *cobra.Command {
+	return &cobra.Command{
+		Use:   "health",
+		Short: "Check server health",
+		Long:  "Check the health status of the mc-proxy server.",
+		RunE: func(cmd *cobra.Command, args []string) error {
+			client := clientFromContext(cmd.Context())
+
+			ctx, cancel := context.WithTimeout(cmd.Context(), 5*time.Second)
+			defer cancel()
+
+			status, err := client.CheckHealth(ctx)
+			if err != nil {
+				return fmt.Errorf("checking health: %w", err)
+			}
+
+			fmt.Println(status)
+
+			if status != mcproxy.HealthServing {
+				return fmt.Errorf("server is not healthy")
+			}
+
+			return nil
+		},
+	}
+}