feat: 实现时间流动完整逻辑并同步 HUD 显示

- TimeSystem 支持月/年进位，仅游戏场景推进
- HUD 时间标签订阅 day_passed 实时更新
- 新游戏时重置年月日

src/Core/TimeSystem.gd

@@ -3,25 +3,36 @@ extends Node
 signal day_passed(year, month, day)
 
 const SPEEDS := [1.0, 5.0, 20.0]
-var speed_index := 0
+const DAYS_PER_MONTH := 30
+const MONTHS_PER_YEAR := 12
 
-const DAY_LENGTH := 5.0
+var speed_index := 0
+const DAY_LENGTH := 0.5
 var speed := 1.0
 var paused := false
 var _elapsed := 0.0
 
 func _process(delta: float) -> void:
-	if paused:
+	if paused or not _is_in_game():
 		return
 	_elapsed += delta * speed
 	if _elapsed >= DAY_LENGTH:
 		_elapsed -= DAY_LENGTH
 		_advance()
 
+func _is_in_game() -> bool:
+	var scene := get_tree().current_scene
+	return scene != null and scene.name == "MainGame"
+
 func _advance() -> void:
-	# GameState.year, GameState.month, GameState.day 推进
-	GameState.day = GameState.day + 1;
-	day_passed.emit()
+	GameState.day += 1
+	if GameState.day > DAYS_PER_MONTH:
+		GameState.day = 1
+		GameState.month += 1
+		if GameState.month > MONTHS_PER_YEAR:
+			GameState.month = 1
+			GameState.year += 1
+	day_passed.emit(GameState.year, GameState.month, GameState.day)
 
 func cycle_speed() -> float:
 	speed_index = (speed_index + 1) % SPEEDS.size()
@@ -38,3 +49,9 @@ func toggle_pause() -> bool:
 
 func get_speed_label() -> String:
 	return "x%d" % int(speed)
+
+func get_current_date() -> Array:
+	return [GameState.year, GameState.month, GameState.day]
+
+func get_date_text() -> String:
+	return "%d年 %d月 %d日" % [GameState.year, GameState.month, GameState.day]