存档重构，游戏内容解锁机制；教程完善（未完成）

Assets/Scripts/Menu/InformationTransistor.cs

@@ -7,12 +7,26 @@ using UnityEngine.Serialization;
 
 namespace Ichni
 {
+    /// <summary>
+    /// GameScene 返回 MenuScene 后应恢复的页面。
+    /// 该枚举替代互斥的布尔标记，避免普通歌曲与教程返回状态同时残留。
+    /// </summary>
+    public enum MenuReturnDestination
+    {
+        None,
+        SongSelection,
+        Story
+    }
+
     public class InformationTransistor : MonoBehaviour
     {
         public static InformationTransistor instance;
-        
-        public bool isReturnedFromGame;
-        public bool isReturnedFromTutorial;
+
+        /// <summary>
+        /// 当前游戏运行结束后，MenuScene 应恢复的唯一目标页面。
+        /// 运行期间保存在 DontDestroyOnLoad 对象中，不写入玩家存档。
+        /// </summary>
+        public MenuReturnDestination menuReturnDestination;
 
         public ChapterSelectionUnit chapter;
         public SongItemData song;
@@ -30,8 +44,7 @@ namespace Ichni
             {
                 instance = this;
                 DontDestroyOnLoad(gameObject);
-                isReturnedFromGame = false;
-                isReturnedFromTutorial = false;
+                menuReturnDestination = MenuReturnDestination.None;
             }
             else
             {
@@ -42,11 +55,48 @@ namespace Ichni
         public void SetInformation(ChapterSelectionUnit chapter,
             SongItemData song, DifficultyData difficulty)
         {
+            // 保留旧入口，供现有选曲流程在播放过场前预先写入歌曲信息。
+            // 真正进入 GameScene 时，MenuManager.EnterGame 会补充 SongSelection 返回目标。
+            PrepareGameLaunch(chapter, song, difficulty, MenuReturnDestination.None);
+        }
+
+        /// <summary>
+        /// 统一准备一次 GameScene 运行所需的上下文。
+        /// 普通选曲和 TutorialBlock 都必须通过此入口写入，防止章节、歌曲、难度与返回目标来自不同旧运行。
+        /// </summary>
+        public bool PrepareGameLaunch(ChapterSelectionUnit chapter, SongItemData song,
+            DifficultyData difficulty, MenuReturnDestination returnDestination)
+        {
+            if (chapter == null || song == null || difficulty == null)
+            {
+                Debug.LogWarning("[InformationTransistor] 缺少章节、歌曲或难度，无法准备 GameScene 上下文。");
+                return false;
+            }
+
             this.chapter = chapter;
             this.song = song;
             this.difficulty = difficulty;
-            this.chapterSwitch = chapter.chapterSwitch;
-            this.songSwitch = song.songSwitch;
+            chapterSwitch = chapter.chapterSwitch;
+            songSwitch = song.songSwitch;
+            menuReturnDestination = returnDestination;
+            return true;
+        }
+
+        /// <summary>
+        /// 由现有选曲过场在真正激活 GameScene 前设置返回目标。
+        /// </summary>
+        public void SetMenuReturnDestination(MenuReturnDestination returnDestination)
+        {
+            menuReturnDestination = returnDestination;
+        }
+
+        /// <summary>
+        /// MenuScene 已依据返回目标完成恢复后调用。
+        /// 只清除一次性路由，不清除歌曲与难度，以免当前 UI 的运行时缓存被意外破坏。
+        /// </summary>
+        public void ClearMenuReturnDestination()
+        {
+            menuReturnDestination = MenuReturnDestination.None;
         }
     }
-}
+}