存档重构，游戏内容解锁机制；教程完善（未完成）

Assets/Scripts/Menu/MenuManager.cs

@@ -3,10 +3,13 @@ using System.Collections;
 using System.Collections.Generic;
 using AK.Wwise;
 using Ichni.Menu;
+using Ichni.Menu.UI;
+using Ichni.Story;
 using Ichni.Story.UI;
 using Ichni.UI;
 using Sirenix.OdinInspector;
 using SLSUtilities.WwiseAssistance;
+using UniRx;
 using UnityEngine;
 using UnityEngine.SceneManagement;
 using UnityEngine.Serialization;
@@ -21,6 +24,7 @@ namespace Ichni
         public LoginPage loginPage;
         public ChapterSelectionUIPage chapterSelectionUIPage;
         public StoryUIPage storyUIPage;
+        public SelectionBoxUIPage selectionBoxUIPage;
         // dialogUIPage 已随旧对话系统移除；阶段 3 将接入新的 VN 对话页面引用
         public SongSelectionUIPage songSelectionUIPage;
         public TransitionUIPage transitionUIPage;
@@ -34,6 +38,12 @@ namespace Ichni
     {
         AsyncOperation asyncOperation;
         public bool isEnteringGame;
+
+        /// <summary>
+        /// 当前 MenuScene 是否已经完成 GameScene 预加载且尚未处于切场中。
+        /// TutorialFlowController 在写入“已处理”剧情变量前使用此状态进行最后一次启动前检查。
+        /// </summary>
+        public bool CanBeginGame => !isEnteringGame && asyncOperation != null;
         
         private void Awake()
         {
@@ -44,24 +54,39 @@ namespace Ichni
         {
             isEnteringGame = false;
             
-            if (InformationTransistor.instance.isReturnedFromGame)
+            InformationTransistor information = InformationTransistor.instance;
+            MenuReturnDestination returnDestination = information != null
+                ? information.menuReturnDestination
+                : MenuReturnDestination.None;
+
+            if (returnDestination == MenuReturnDestination.SongSelection &&
+                information != null && information.chapter != null &&
+                information.song != null && information.difficulty != null)
             {
                 startUIPage.mainCanvasGroup.gameObject.SetActive(false);
                 ChapterSelectionManager.instance.currentChapter = 
-                    InformationTransistor.instance.chapter;
+                    information.chapter;
                 AudioManager.SetSwitch(ChapterSelectionManager.instance.currentChapter.chapterSwitch);
-                MenuInformationRecorder.instance.songSelectionRecords.Add(
-                    ChapterSelectionManager.instance.currentChapter, 
-                    new SongSelectionRecord(InformationTransistor.instance.song, InformationTransistor.instance.difficulty));
+                MenuInformationRecorder.instance.songSelectionRecords[
+                    ChapterSelectionManager.instance.currentChapter] =
+                    new SongSelectionRecord(information.song, information.difficulty);
                 songSelectionUIPage.FadeIn();
             }
-            else if (InformationTransistor.instance.isReturnedFromTutorial)
+            else if (returnDestination == MenuReturnDestination.Story &&
+                     information != null && information.chapter != null)
             {
                 startUIPage.mainCanvasGroup.gameObject.SetActive(false);
-                ChapterSelectionManager.instance.currentChapter = InformationTransistor.instance.chapter;
+                ChapterSelectionManager.instance.currentChapter = information.chapter;
                 AudioManager.SetSwitch(ChapterSelectionManager.instance.currentChapter.chapterSwitch);
+
+                // MenuScene 会在教程游玩后重新创建，必须显式重建章节故事树，
+                // 不能依赖旧场景中残留的 Block 实例。
+                StoryManager.instance?.OpenChapter(ChapterSelectionManager.instance.currentChapter.chapterIndex);
                 storyUIPage.FadeIn();
             }
+
+            // 返回目标是一次性运行态信息。无论是否能恢复页面，都不能让它在下次重进菜单时重复生效。
+            information?.ClearMenuReturnDestination();
             
             Application.targetFrameRate = SettingsManager.instance.gameSettings.targetFrame;
             asyncOperation = SceneManager.LoadSceneAsync("GameScene");
@@ -73,15 +98,59 @@ namespace Ichni
     {
         public void EnterGame()
         {
-            InformationTransistor.instance.isReturnedFromTutorial = false;
-            InformationTransistor.instance.isReturnedFromGame = true;
+            EnterGame(MenuReturnDestination.SongSelection);
+        }
+
+        /// <summary>
+        /// 激活已预加载的 GameScene，并写入唯一的菜单返回目标。
+        /// 普通选曲使用 <see cref="MenuReturnDestination.SongSelection"/>，教程使用
+        /// <see cref="MenuReturnDestination.Story"/>。
+        /// </summary>
+        public void EnterGame(MenuReturnDestination returnDestination)
+        {
+            InformationTransistor.instance?.SetMenuReturnDestination(returnDestination);
             EnterGameScene();
         }
+
+        /// <summary>
+        /// 为 TutorialBlock 等非选曲入口准备上下文并播放通用转场。
+        /// 运行成功后会返回 true；返回 false 时不会修改剧情变量或存档，调用方应保留原状。
+        /// </summary>
+        public bool TryBeginGame(ChapterSelectionUnit chapter, SongItemData song,
+            DifficultyData difficulty, MenuReturnDestination returnDestination, UIPageBase sourcePage)
+        {
+            if (!CanBeginGame)
+            {
+                Debug.LogWarning("[MenuManager] GameScene 未完成预加载或菜单已在切换，忽略启动请求。");
+                return false;
+            }
+
+            if (InformationTransistor.instance == null ||
+                !InformationTransistor.instance.PrepareGameLaunch(chapter, song, difficulty, returnDestination))
+            {
+                return false;
+            }
+
+            isEnteringGame = true;
+            sourcePage?.FadeOut();
+            transitionUIPage?.FadeIn();
+            AudioManager.Post(AK.EVENTS.ENTERTOGAME);
+
+            Observable.Timer(TimeSpan.FromSeconds(0.6f)).Subscribe(_ => EnterGameScene());
+            return true;
+        }
         
         public void EnterGameScene()
         {
-            MenuInputManager.instance.gameInput.Menu.Disable();
+            if (asyncOperation == null)
+            {
+                Debug.LogError("[MenuManager] GameScene 尚未完成预加载，无法进入游戏。");
+                isEnteringGame = false;
+                return;
+            }
+
+            MenuInputManager.instance?.gameInput?.Menu.Disable();
             asyncOperation.allowSceneActivation = true;
         }
     }
-}
+}