feat: add vmux setup and vmux hook for Claude Code integration

- vmux setup: idempotently adds hooks to ~/.claude/settings.json
- vmux hook: receives Claude Code hook events via env vars and forwards to daemon
- Daemon handles "hook" action on Unix socket (no HTTP server needed)
- Hooks provide instant state detection (permission/question/idle)

main.go

@@ -148,6 +148,18 @@ func main() {
 		}
 		runI3Bar(sockPath)
 
+	case "hook":
+		event := parseHookEnv()
+		if event.HookEventName == "" {
+			os.Exit(0)
+		}
+		client := NewClient(sockPath)
+		hookArgs, _ := json.Marshal(event)
+		client.Send(Request{Action: "hook", Args: hookArgs})
+
+	case "setup":
+		runSetup()
+
 	case "daemon":
 		runDaemon(sockPath)
 
@@ -208,8 +220,8 @@ Commands:
   label <id> <text> Assign a label to a session
   focus <minutes>   Suppress notifications for N minutes
   i3bar             Output i3bar JSON (use as status_command in i3 config)
+  setup             Add vmux hooks to Claude Code settings (idempotent)
   stop              Stop the vmux daemon
-  daemon            Run the daemon in foreground (used internally)
 
 Flags:
   --no-color        Disable colored output