feat: 优化开始训练指引并修复AI递归问题

- 修复 GameController._trigger_ai 中AI决策递归调用问题，增加 _is_processing 锁
- 修复 TrainingController 未加入场景树导致信号无法触发的问题
- 主菜单添加"游戏说明"按钮和详细指引对话框
- 训练室添加引导提示标签和操作状态反馈
- 优化提示功能显示中文牌型名称（单张、对子、顺子等）
- 优化错误信息显示，提供更具体的失败原因
- 清除调试 print 语句

🤖 Generated with [Qoder][https://qoder.com]

src/ui/scenes/training_room.gd

@@ -7,6 +7,7 @@ var controller: TrainingController
 @onready var pass_button: Button = $Buttons/PassButton
 @onready var hint_button: Button = $Buttons/HintButton
 @onready var status_label: Label = $StatusLabel
+@onready var guide_label: Label = $GuideLabel
 
 func _ready() -> void:
 	play_button.pressed.connect(_on_play_pressed)
@@ -16,54 +17,98 @@ func _ready() -> void:
 
 func start_training() -> void:
 	controller = TrainingController.new()
+	add_child(controller)
 	hand_area.training_controller = controller
 	controller.start_game(Config.rule_config, 0)
 	controller.turn_ready.connect(_on_turn_ready)
 	controller.state_changed.connect(_refresh_ui)
 	controller.game_ended.connect(_on_game_ended)
+	_update_guide_text()
 	_refresh_ui()
 
+func _update_guide_text() -> void:
+	if guide_label:
+		guide_label.text = "💡 提示：点击手牌选中，然后点击「出牌」或「过牌」。首次出牌建议点击「提示」按钮。"
+
 func _on_turn_ready(player_idx: int, is_human: bool) -> void:
 	if is_human:
 		hand_area.enable_input()
-		if status_label: status_label.text = "你的回合"
+		if status_label:
+			status_label.text = "你的回合 - 请出牌或点击过牌"
 	else:
 		hand_area.disable_input()
 		if status_label and controller and controller.game_state:
 			status_label.text = "%s 思考中..." % controller.game_state.player_names[player_idx]
 
 func _on_play_pressed() -> void:
-	if not hand_area: return
+	if not hand_area:
+		return
 	var selected := hand_area.selected_cards
 	if selected.is_empty():
+		if status_label:
+			status_label.text = "请先选择要出的牌"
 		return
 	var result := controller.handle_human_play(selected)
 	if not result.ok:
-		if status_label: status_label.text = "无效出牌"
+		var error_msg := _get_error_message(result.error_code)
+		if status_label:
+			status_label.text = "❌ %s" % error_msg
 		return
 	hand_area.clear_selection()
+	if status_label:
+		status_label.text = "✓ 出牌成功！"
 	_refresh_ui()
 
+func _get_error_message(error_code: int) -> String:
+	match error_code:
+		1: return "无效的牌型组合"
+		2: return "不是你的回合"
+		3: return "不能过牌（你是领出者）"
+		4: return "牌不在手中"
+		_: return "出牌失败"
+
 func _on_pass_pressed() -> void:
 	var result := controller.handle_human_pass()
 	if not result.ok:
-		if status_label: status_label.text = "不能过牌"
+		var error_msg := _get_error_message(result.error_code)
+		if status_label:
+			status_label.text = "❌ %s" % error_msg
 		return
+	if status_label:
+		status_label.text = "✓ 已过牌"
 	_refresh_ui()
 
 func _on_hint_pressed() -> void:
 	var hint := controller.get_hint()
 	if hint == null or hint.type == -1:
-		if status_label: status_label.text = "建议：过牌"
+		if status_label:
+			status_label.text = "建议：过牌（当前轮到你领出，但无合适牌型）"
+		return
+	if not hand_area:
 		return
-	if not hand_area: return
 	hand_area.clear_selection()
 	for card in hint.cards:
 		for cn in hand_area.card_nodes:
 			if cn.card_data != null and cn.card_data.card_id == card.card_id:
 				cn.set_selected(true)
 				hand_area.selected_cards.append(card)
-	if status_label: status_label.text = "建议牌型: %s (rank=%d)" % [hint.type, hint.primary_rank]
+	var type_name := _get_type_name(hint.type)
+	if status_label:
+		status_label.text = "💡 建议：出 %s（%d张，主阶=%d）" % [type_name, hint.cards.size(), hint.primary_rank]
+
+func _get_type_name(type_idx: int) -> String:
+	match type_idx:
+		0: return "单张"
+		1: return "对子"
+		2: return "三张"
+		3: return "三带二"
+		4: return "顺子"
+		5: return "连对"
+		6: return "钢板"
+		7: return "同花顺"
+		8: return "炸弹"
+		9: return "火箭"
+		_: return "未知"
 
 func _on_game_ended(winner_team: int, _reason: String) -> void:
 	if status_label: status_label.text = "游戏结束! 队伍 %d 获胜" % winner_team
@@ -72,7 +117,4 @@ func _on_game_ended(winner_team: int, _reason: String) -> void:
 func _refresh_ui() -> void:
 	if controller and controller.game_state and hand_area:
 		var hand: Array = controller.game_state.get_hand(0)
-		print("[DEBUG] _refresh_ui: hand size = ", hand.size())
 		hand_area.update_hand(hand)
-	else:
-		print("[DEBUG] _refresh_ui: controller=", controller, " game_state=", controller.game_state if controller else null, " hand_area=", hand_area)