refactor(enemy): Boss 选招与战利品掉落改用 WeightedPick;删除零调用的 SelectWeightedSkill 死代码

Assets/_Game/Scripts/Enemies/LootResolver.cs

@@ -33,32 +33,24 @@ namespace BaseGames.Enemies
             bool isHard = dm != null &&
                           (int)dm.CurrentLevel >= (int)DifficultyLevel.Hard;
 
-            float totalWeight = 0f;
-            foreach (var entry in table.Entries)
+            // 有效权重只算一遍（难度加成），再交由共享原语加权抽取；无正权重时不掉落。
+            var weights = new float[table.Entries.Length];
+            for (int i = 0; i < table.Entries.Length; i++)
             {
+                var entry = table.Entries[i];
                 float w = entry.BaseWeight;
                 if (isHard && entry.ScaleWithDifficulty) w *= 1.5f;
-                totalWeight += w;
+                weights[i] = w;
             }
 
-            if (totalWeight <= 0f) return;
+            int idx = WeightedPick.Index(weights);
+            if (idx < 0) return;
 
-            float roll = Random.Range(0f, totalWeight);
-            float accum = 0f;
-            foreach (var entry in table.Entries)
-            {
-                float w = entry.BaseWeight;
-                if (isHard && entry.ScaleWithDifficulty) w *= 1.5f;
-                accum += w;
-                if (roll <= accum)
-                {
-                    if (!string.IsNullOrEmpty(entry.ItemId))
-                        CollectibleSpawner.SpawnItem(worldPosition, entry.ItemId);
-                    else if (entry.LingZhuAmount > 0)
-                        CollectibleSpawner.SpawnLingZhu(worldPosition, entry.LingZhuAmount);
-                    return;
-                }
-            }
+            var picked = table.Entries[idx];
+            if (!string.IsNullOrEmpty(picked.ItemId))
+                CollectibleSpawner.SpawnItem(worldPosition, picked.ItemId);
+            else if (picked.LingZhuAmount > 0)
+                CollectibleSpawner.SpawnLingZhu(worldPosition, picked.LingZhuAmount);
         }
 
         private static void ApplyDifficultyLingZhuScale(ref int lingZhu)