Port the CLI to Go: awg-control <start|stop|…>

internal/cli reimplements cli/src: start/stop/restart/status with the
awg-ctrl health gate, credentials, join/unjoin, peers [drop], monitor
install/status/remove and the interactive menu. Same cli.env, pid files,
logs and messages. Without arguments or with an operator command the binary
acts as the CLI; ctrl/ui/agent stay service roles.

- services are started as the same binary (`awg-control ctrl|ui|agent`),
  detached into their own session, from the same working directories
- processes started by the Node CLI (tsx … index.ts / server.ts) are still
  recognised, so `stop` and `status` work across the switch
- after join the fresh restart gets the original environment, so a rejoin
  picks up the new cli.env instead of the inherited old CORE_* values
- install root: AWG_ROOT, else the nearest parent of the binary with cli/ or
  .env, else /opt/awg-control

Checked end to end on stubbed awg: start/status/stop, credentials, join to
the panel's own hub (with and without --no-panel), peers listing and drop,
unjoin, menu.

cmd/awg-control/main.go

@@ -9,14 +9,16 @@ import (
 	"syscall"
 
 	"github.com/maeneko/forgetting/internal/agent"
+	"github.com/maeneko/forgetting/internal/cli"
 	"github.com/maeneko/forgetting/internal/ctrl"
 	"github.com/maeneko/forgetting/internal/ui"
 )
 
 func main() {
+	// Без аргументов или с командой оператора — CLI (меню, start/stop/…), как прежний awg-ctrl.
 	if len(os.Args) < 2 {
-		fmt.Fprintln(os.Stderr, "usage: awg-control <ctrl|ui|agent|start|stop|restart|status|…>")
-		os.Exit(1)
+		cli.Main(nil)
+		return
 	}
 	switch os.Args[1] {
 	case "ctrl":
@@ -54,7 +56,6 @@ func main() {
 		defer stop()
 		a.Run(ctx)
 	default:
-		fmt.Fprintf(os.Stderr, "awg-control: неизвестная команда %q\n", os.Args[1])
-		os.Exit(1)
+		cli.Main(os.Args[1:])
 	}
 }