refactor: Round 53 remove all legacy backward-compatibility code

- QuestSO: remove giverNpcId, prerequisiteQuests/Flags/FlagsLogic, failCondition,
  conditionFlags, npcDialogueKey fields; simplify GiverNpcId property to giverNpc?.npcId;
  clean ValidatePrerequisiteCycles/HasPrerequisiteCycle to use prerequisites.questDependencies;
  remove ValidateBranchDialogueKeys migration warning block; clean QuestPrerequisite doc
- QuestManager: remove OnLoad DataVersion 1/2 migration paths (ProgressCounts, hasNewFormat/
  useNewFormat); remove CheckQuestDepsAndFlags old-field fallback (prerequisiteQuests/Flags);
  remove UnlockBranches conditionFlags fallback; remove DispatchEvent failCondition fallback;
  fix ValidatePrerequisites DFS to scan prerequisites.questDependencies
- SaveData: remove ProgressCounts (Obsolete), ObjectiveIndex (unused), GiverNpcId (never
  written) fields from QuestState; simplify DataVersion doc comment
- QuestSOEditor: replace migration-only editor with minimal DrawDefaultInspector
- QuestModule: update all prerequisiteQuests/conditionFlags/npcDialogueKey/failCondition
  references to canonical new fields; update ValidateBranchFlags check 10
- FlagAuditModule: replace conditionFlags/prerequisiteFlags scans with conditionFlagEntries/
  prerequisites.flagCondition.flags
- NpcSO: remove QuestSO.giverNpcId reference from npcId tooltip
- NpcAffinityEvent/RewardSO: update doc comments to reference giverNpc instead of giverNpcId

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Assets/_Game/Scripts/Core/Save/SaveData.cs

@@ -134,31 +134,20 @@ namespace BaseGames.Core.Save
     [Serializable]
     public class QuestState
     {
-        /// <summary>
-        /// 此 QuestState 数据格式版本号。
-        ///   1 = 原始格式（ProgressCounts 按索引，已弃用）
-        ///   2 = Round 24+ 格式（ObjectiveProgress 按 objectiveId 键值对）
-        ///   3 = Round 52+ 格式（新增 ObjectiveCompleted、StartedAtUtc、CompletedAtUtc）
-        /// OnLoad 按此字段显式选择解析路径，杜绝依赖 Count > 0 的隐式推断。
-        /// </summary>
+        /// <summary>此 QuestState 数据格式版本号，固定为 3。</summary>
         public int         DataVersion       = 3;
         /// <summary>任务运行时状态字符串。有效值：Unavailable|Available|Active|Paused|Completed|Failed。
         /// OnLoad 通过 Enum.TryParse 解析；无效值将触发开发模式警告并降级为 Unavailable。</summary>
         public string      Status;
-        public int         ObjectiveIndex;
-        /// <summary>新格式（DataVersion≥2）：objectiveId → progressCount，重排目标顺序后存档不会错位。</summary>
+        /// <summary>objectiveId → progressCount，重排目标顺序后存档不会错位。</summary>
         public Dictionary<string, int> ObjectiveProgress = new();
         /// <summary>各目标是否已判定完成（objectiveId → completed）。
-        /// 防止 GetRequiredCount 在版本迭代中变更后，重新计算结果与存档实际状态不一致。DataVersion≥3 写入。</summary>
+        /// 防止 GetRequiredCount 在版本迭代中变更后，重新计算结果与存档实际状态不一致。</summary>
         public Dictionary<string, bool> ObjectiveCompleted = new();
-        /// <summary>任务接取时间（Unix 秒时间戳，UTC）。0 = 未记录（旧存档）。DataVersion≥3 写入。</summary>
+        /// <summary>任务接取时间（Unix 秒时间戳，UTC）。0 = 未记录，跳过。</summary>
         public long        StartedAtUtc;
-        /// <summary>任务完成时间（Unix 秒时间戳，UTC）。0 = 未完成或未记录。DataVersion≥3 写入。</summary>
+        /// <summary>任务完成时间（Unix 秒时间戳，UTC）。0 = 未完成或未记录。</summary>
         public long        CompletedAtUtc;
-        /// <summary>旧格式（按数组索引，DataVersion=1）：仅用于迁移旧版存档，新存档不再写入。已弃用，将在后续版本移除。</summary>
-        [System.Obsolete("旧格式存档兼容字段，仅供 OnLoad DataVersion=1 迁移使用。新存档改用 ObjectiveProgress（objectiveId 键值对）。")]
-        public List<int>   ProgressCounts = new();
-        public string      GiverNpcId;
     }
 
     // ─── Achievements ─────────────────────────────────────────────────────────