补全 CombatNode 逻辑 + 重构 EnemyManager

- 添加了关卡内的难度系数与掉落
    - 难度系数：每循环一轮波次敌人血量翻倍
    - 道具掉落：按照掉落概率曲线根据波次计算当前爆率，并从新增的道具池里选择道具
    - `CombatResourceManager`：统一维护关卡内资源状态（硬币/金币/道具掉落）
- 重构 `EnemyManager`：
    - `EnemyManager`：编排子服务，不承载具体业务细节
    - `EnemySpawnDirector`：管理刷怪时序
    - `SpawnerResolver`：管理出生点与路径
    - `EnemyLifecycleTracker`：追踪敌人生命周期
    - `EnemyConfigService`：管理敌人配置与倍率

Assets/GameMain/Scripts/Event/Combat/CombatEnemyHpRateChangedEventArgs.cs

@@ -0,0 +1,31 @@
+using GameFramework;
+using GameFramework.Event;
+
+namespace GeometryTD.CustomEvent
+{
+    public class CombatEnemyHpRateChangedEventArgs : GameEventArgs
+    {
+        public static int EventId => typeof(CombatEnemyHpRateChangedEventArgs).GetHashCode();
+
+        public override int Id => EventId;
+
+        public int EnemyHpRateMultiplier { get; private set; }
+
+        public CombatEnemyHpRateChangedEventArgs()
+        {
+            EnemyHpRateMultiplier = 1;
+        }
+
+        public static CombatEnemyHpRateChangedEventArgs Create(int enemyHpRateMultiplier)
+        {
+            var args = ReferencePool.Acquire<CombatEnemyHpRateChangedEventArgs>();
+            args.EnemyHpRateMultiplier = enemyHpRateMultiplier > 0 ? enemyHpRateMultiplier : 1;
+            return args;
+        }
+
+        public override void Clear()
+        {
+            EnemyHpRateMultiplier = 1;
+        }
+    }
+}

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