refactor: HUD 节点改用唯一名称引用，场景识别改用分组

- TopBarHUD 用 @onready + % 唯一名称替代硬编码路径
- TimeSystem 用 game_scene 分组替代场景名字符串比较

src/Core/MainGame.tscn

@@ -4,6 +4,7 @@
 [ext_resource type="PackedScene" uid="uid://dl0tb68vsw3c6" path="res://src/UI/HUD/TopBarHUD.tscn" id="1_g6xmk"]
 
 [node name="MainGame" type="Node" unique_id=2053561265]
+groups = ["game_scene"]
 script = ExtResource("1_8bu23")
 
 [node name="TopBarHud" parent="." unique_id=1115394694 instance=ExtResource("1_g6xmk")]

src/Core/TimeSystem.gd

@@ -51,9 +51,10 @@ func _process(delta: float) -> void:
 
 
 ## 判断当前场景是否为游戏世界场景（主菜单/存档界面不推进时间）。
+## 通过 "game_scene" 分组识别，而非场景名。
 func _is_in_game() -> bool:
 	var scene := get_tree().current_scene
-	return scene != null and scene.name == "MainGame"
+	return scene != null and scene.is_in_group("game_scene")
 
 
 ## 推进一日并广播对应信号，跨月/跨年时补发 month_passed / year_passed。

src/UI/HUD/TopBarHUD.tscn

@@ -49,6 +49,7 @@ size_flags_horizontal = 3
 size_flags_vertical = 8
 size_flags_stretch_ratio = 2.0
 label_settings = SubResource("LabelSettings_bn2o5")
+unique_name_in_owner = true
 
 [node name="Label_Reputation" type="Label" parent="HBoxContainer" unique_id=985110673]
 layout_mode = 2
@@ -74,6 +75,7 @@ layout_mode = 2
 theme_override_fonts/font = ExtResource("1_pa2rn")
 theme_override_font_sizes/font_size = 32
 text = "暂停"
+unique_name_in_owner = true
 
 [node name="Button_Speed1" type="Button" parent="HBoxContainer/SpeedGroup" unique_id=2144893128]
 custom_minimum_size = Vector2(48, 0)
@@ -81,6 +83,7 @@ layout_mode = 2
 theme_override_fonts/font = ExtResource("1_pa2rn")
 theme_override_font_sizes/font_size = 32
 text = "1x"
+unique_name_in_owner = true
 
 [node name="Button_Speed5" type="Button" parent="HBoxContainer/SpeedGroup" unique_id=2144893129]
 custom_minimum_size = Vector2(48, 0)
@@ -88,6 +91,7 @@ layout_mode = 2
 theme_override_fonts/font = ExtResource("1_pa2rn")
 theme_override_font_sizes/font_size = 32
 text = "5x"
+unique_name_in_owner = true
 
 [node name="Button_Speed20" type="Button" parent="HBoxContainer/SpeedGroup" unique_id=2144893130]
 custom_minimum_size = Vector2(48, 0)
@@ -95,6 +99,7 @@ layout_mode = 2
 theme_override_fonts/font = ExtResource("1_pa2rn")
 theme_override_font_sizes/font_size = 32
 text = "20x"
+unique_name_in_owner = true
 
 [node name="placeholder_1" type="Label" parent="HBoxContainer" unique_id=1042446504]
 layout_mode = 2

src/UI/HUD/top_bar_hud.gd

@@ -5,24 +5,25 @@ extends Control
 ## 请求返回主菜单。
 signal sign_return_mainmenu
 
-## 三个流速按钮的节点名（与 tscn 中的 SpeedGroup 子节点对应）。
-const SPEED_BUTTONS := ["Button_Speed1", "Button_Speed5", "Button_Speed20"]
 ## 激活档位按钮颜色。
 const ACTIVE_COLOR := Color(1.0, 1.0, 1.0)
 ## 未激活档位按钮颜色。
 const INACTIVE_COLOR := Color(0.55, 0.55, 0.55)
 
+@onready var time_label: Label = %Value_Time
+@onready var pause_button: Button = %Button_Pause
+@onready var speed_buttons: Array[Button] = [%Button_Speed1, %Button_Speed5, %Button_Speed20]
+
 func _ready() -> void:
-	for i in SPEED_BUTTONS.size():
-		var btn: Button = $HBoxContainer/SpeedGroup.get_node(SPEED_BUTTONS[i])
-		btn.button_up.connect(_on_speed_button_up.bind(i))
+	for i in speed_buttons.size():
+		speed_buttons[i].button_up.connect(_on_speed_button_up.bind(i))
 	TimeSystem.day_passed.connect(_on_day_passed)
 	_update_speed_ui()
-	$HBoxContainer/Value_Time.text = TimeSystem.get_date_text()
+	time_label.text = TimeSystem.get_date_text()
 
 ## 每日推进时刷新日期显示。
 func _on_day_passed(_year: int, _month: int, _day: int) -> void:
-	$HBoxContainer/Value_Time.text = TimeSystem.get_date_text()
+	time_label.text = TimeSystem.get_date_text()
 
 ## 点击"返回"按钮。
 func _on_button_return_button_up() -> void:
@@ -41,9 +42,7 @@ func _on_speed_button_up(index: int) -> void:
 
 ## 刷新速度组 UI：暂停按钮文字与各档位高亮状态。
 func _update_speed_ui() -> void:
-	var pause_btn: Button = $HBoxContainer/SpeedGroup/Button_Pause
-	pause_btn.text = "继续" if TimeSystem.paused else "暂停"
-	for i in SPEED_BUTTONS.size():
-		var btn: Button = $HBoxContainer/SpeedGroup.get_node(SPEED_BUTTONS[i])
+	pause_button.text = "继续" if TimeSystem.paused else "暂停"
+	for i in speed_buttons.size():
 		var active := (i == TimeSystem.speed_index) and not TimeSystem.paused
-		btn.modulate = ACTIVE_COLOR if active else INACTIVE_COLOR
+		speed_buttons[i].modulate = ACTIVE_COLOR if active else INACTIVE_COLOR