refactor 5:

- MapData.cs 现在会携带战斗初始上下文：
    - InitialCoin
    - 建塔 TowerStatsData 快照
    - TryConsumeCoin / AddCoin 运行时回调
- CombatLoadingState.cs 负责从 CombatInRunResourceManager 读取 coin 和 build stats 快照，组装 MapData 后再交给加载链。
- CombatLoadSession.cs 改成接收外部构造好的 MapData，不再自己只塞一个 LevelId。
- CombatScheduler.cs 不再在 Start() 里直接发起地图加载，加载细节回到 CombatLoadingState。
- MapEntity.cs 已经不再直接读 GameEntry.CombatNode 的 coin / build count / build stats，也不再通过它做 coin 读写：
    - 初始 coin 和 build stats 从 MapData 读取
    - 后续 coin 通过 CombatCoinChangedEventArgs 同步
    - 建塔/升级/拆塔时的 coin 变更通过 MapData 注入回调执行

Assets/GameMain/Scripts/Entity/EntityLogic/MapEntity.cs

@@ -1,6 +1,8 @@
 using System;
 using System.Collections.Generic;
 using GeometryTD.CustomComponent;
+using GeometryTD.CustomEvent;
+using GameFramework.Event;
 using GeometryTD.Map;
 using GeometryTD.Definition;
 using GeometryTD.Entity.EntityData;
@@ -37,6 +39,8 @@ namespace GeometryTD.Entity
         private TowerSelectionPresenter _towerSelectionPresenter;
         
         private CombatSelectUseCaseConfigurator _combatSelectUseCaseConfigurator;
+        private int _currentCoin;
+        private bool _isCoinEventSubscribed;
 
         public IReadOnlyList<Vector3Int> PathCells => _mapTopologyService != null
             ? _mapTopologyService.PathCells
@@ -117,6 +121,11 @@ namespace GeometryTD.Entity
             {
                 Log.Warning("MapData is invalid for map entity '{0}'.", Id);
             }
+            else
+            {
+                _currentCoin = Mathf.Max(0, _mapData.InitialCoin);
+                SubscribeCombatEvents();
+            }
 
             RefreshTiles();
             ConfigureCombatSelectUseCase();
@@ -125,6 +134,7 @@ namespace GeometryTD.Entity
 
         protected override void OnHide(bool isShutdown, object userData)
         {
+            UnsubscribeCombatEvents();
             HideCombatSelectForm();
             _towerPlacementService?.HideAndClearAllPlacedTowers();
             ClearSelectionState();
@@ -301,8 +311,7 @@ namespace GeometryTD.Entity
                 return false;
             }
 
-            CombatNodeComponent combatNode = GameEntry.CombatNode;
-            if (combatNode == null || !combatNode.TryGetBuildTowerStats(buildIndex, out TowerStatsData buildTowerStats))
+            if (_mapData == null || !_mapData.TryGetBuildTowerStats(buildIndex, out TowerStatsData buildTowerStats))
             {
                 return false;
             }
@@ -376,17 +385,49 @@ namespace GeometryTD.Entity
             GameEntry.UIRouter.CloseUI(UIFormType.CombatSelectForm);
         }
 
-        private static int GetCurrentBuildTowerCount()
+        private void SubscribeCombatEvents()
         {
-            if (GameEntry.CombatNode == null)
+            if (_isCoinEventSubscribed)
+            {
+                return;
+            }
+
+            GameEntry.Event.Subscribe(CombatCoinChangedEventArgs.EventId, OnCombatCoinChanged);
+            _isCoinEventSubscribed = true;
+        }
+
+        private void UnsubscribeCombatEvents()
+        {
+            if (!_isCoinEventSubscribed)
+            {
+                return;
+            }
+
+            GameEntry.Event.Unsubscribe(CombatCoinChangedEventArgs.EventId, OnCombatCoinChanged);
+            _isCoinEventSubscribed = false;
+        }
+
+        private void OnCombatCoinChanged(object sender, GameEventArgs e)
+        {
+            if (e is not CombatCoinChangedEventArgs args)
+            {
+                return;
+            }
+
+            _currentCoin = Mathf.Max(0, args.CurrentCoin);
+        }
+
+        private int GetCurrentBuildTowerCount()
+        {
+            if (_mapData == null)
             {
                 return 0;
             }
 
-            return Mathf.Clamp(GameEntry.CombatNode.CurrentBuildTowerCount, 0, 4);
+            return Mathf.Clamp(_mapData.CurrentBuildTowerCount, 0, 4);
         }
 
-        private static bool TryConsumeCoin(int cost)
+        private bool TryConsumeCoin(int cost)
         {
             int requiredCoin = Mathf.Max(0, cost);
             if (requiredCoin <= 0)
@@ -394,27 +435,28 @@ namespace GeometryTD.Entity
                 return true;
             }
 
-            if (GameEntry.CombatNode == null)
+            if (_mapData == null)
             {
                 return false;
             }
 
-            return GameEntry.CombatNode.TryConsumeCoin(requiredCoin);
+            return _mapData.TryConsumeCoin(requiredCoin);
         }
 
-        private static int GetCurrentCoin()
+        private int GetCurrentCoin()
         {
-            return GameEntry.CombatNode != null ? Mathf.Max(0, GameEntry.CombatNode.CurrentCoin) : 0;
+            return Mathf.Max(0, _currentCoin);
         }
 
-        private static void AddCoin(int coin)
+        private void AddCoin(int coin)
         {
             int amount = Mathf.Max(0, coin);
             if (amount <= 0)
             {
                 return;
             }
-            GameEntry.CombatNode?.AddCoin(amount);
+
+            _mapData?.AddCoin(amount);
         }
     }
 }