add audio_manager and code refactoring

core/ai/agents/base/idle_state.gd

@@ -0,0 +1,24 @@
+extends State
+
+@export var wait_time: float = 3.0
+
+var runtime_timer: Timer
+
+func enter() -> void:
+	runtime_timer = Timer.new()
+	runtime_timer.name = "IdleTimer"
+	add_child(runtime_timer)
+	runtime_timer.one_shot = true
+	runtime_timer.timeout.connect(_on_timer_timeout)
+	runtime_timer.start(wait_time)
+
+func exit() -> void:
+	if runtime_timer:
+		if runtime_timer.is_connected("timeout", _on_timer_timeout):
+			runtime_timer.timeout.disconnect(_on_timer_timeout)
+		
+		runtime_timer.queue_free()
+		runtime_timer = null
+
+func _on_timer_timeout() -> void:
+	transitioned.emit(self, "patrol")