fix: Round 54 priority dequeue, onComplete callback, prerequisiteObjectiveId validation, localizationTable guard, FailQuest timestamp, remove empty ValidateBranchDialogueKeys

- DialogueManager.EndDialogue: dequeue by max-priority index instead of FIFO index-0
- DialogueManager.EndDialogue: fire _onCompleteCallback on normal end (was only in ForceEnd)
- NpcSO.OnValidate: auto-restore localizationTable to 'UI' if cleared
- QuestSO.ValidateObjectiveIds: validate prerequisiteObjectiveId references exist in same quest
- QuestSO.OnValidate: remove call to empty ValidateBranchDialogueKeys stub + remove the stub itself
- QuestManager.DispatchEvent toFail loop: write _completedAtUtc timestamp on quest failure

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

Assets/_Game/Scripts/Quest/QuestManager.cs

@@ -1014,6 +1014,7 @@ namespace BaseGames.Quest
                 foreach (var qid in toFail)
                 {
                     _questStates[qid] = QuestStateEnum.Failed;
+                    _completedAtUtc[qid] = System.DateTimeOffset.UtcNow.ToUnixTimeSeconds();
                     _notifiedReadyQuests.Remove(qid);
                     OnQuestStateChanged?.Invoke(qid, QuestStateEnum.Active, QuestStateEnum.Failed);
                     Chan_QuestFailed?.Raise(qid);

Assets/_Game/Scripts/Quest/QuestSO.cs

@@ -118,7 +118,6 @@ namespace BaseGames.Quest
                 s_questIdsCacheTime = -10.0;
             }
 
-            ValidateBranchDialogueKeys();
             ValidateObjectiveIds();
             ValidatePrerequisiteCycles();
             ValidateBranchCycles();
@@ -138,6 +137,17 @@ namespace BaseGames.Quest
                         "在本任务内重复！同一个 ObjectiveSO 资产被引用多次会导致进度互相覆盖，" +
                         "请为每个目标使用独立的 SO 资产。", this);
             }
+
+            // 验证 prerequisiteObjectiveId 引用的 objectiveId 必须存在于本任务中
+            for (int i = 0; i < objectives.Length; i++)
+            {
+                var obj = objectives[i];
+                if (obj == null || string.IsNullOrEmpty(obj.prerequisiteObjectiveId)) continue;
+                if (!seen.Contains(obj.prerequisiteObjectiveId))
+                    Debug.LogError(
+                        $"[QuestSO] '{name}' 的 objectives[{i}].prerequisiteObjectiveId " +
+                        $"'{obj.prerequisiteObjectiveId}' 在本任务中不存在！请检查目标ID是否填写正确。", this);
+            }
         }
 
         /// <summary>
@@ -249,11 +259,6 @@ namespace BaseGames.Quest
             visited.Remove(quest.questId); // 回溯
             return false;
         }
-
-        private void ValidateBranchDialogueKeys()
-        {
-            // npcDialogueSequence 是 SO 直接引用；旧字符串字段已移除。
-        }
 #endif
     }