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/Boss/BossBase.cs

@@ -39,8 +39,9 @@ namespace BaseGames.Enemies
         public int CurrentPhase => _currentPhase;
         private Coroutine _counterStaggerCoroutine;
 
-        // 缓存加权候选列表，避免 UseBossSkillWeighted() 每次 new List → GC 分配
-        private readonly List<(BossSkillSO skill, float w)> _weightedCandidates = new(8);
+        // 缓存加权候选与其有效权重（两者等长、下标对应），避免 UseBossSkillWeighted() 每次 new List → GC 分配
+        private readonly List<BossSkillSO> _weightedCandidates = new(8);
+        private readonly List<float>       _candidateWeights   = new(8);
 
         // 单元素缓冲数组，供 ApplyCounterResponse 缓存当前技能，避免 new[] 分配
         private readonly BossSkillSO[] _singleSkillBuf = new BossSkillSO[1];
@@ -110,31 +111,22 @@ namespace BaseGames.Enemies
 
             // 筛选：在当前阶段可用 + 冷却就绪 + weight > 0
             _weightedCandidates.Clear();
-            float totalWeight = 0f;
+            _candidateWeights.Clear();
             foreach (var s in skills)
             {
                 if (s == null || s.weight <= 0f) continue;
                 if (!_skillExecutor.CanUseSkill(s.skillId)) continue;
                 if (!IsSkillAvailableInPhase(s)) continue;
 
+                _weightedCandidates.Add(s);
                 // 防重复：上一个技能权重打折
-                float w = s.skillId == LastUsedSkillId ? s.weight * 0.3f : s.weight;
-                _weightedCandidates.Add((s, w));
-                totalWeight += w;
+                _candidateWeights.Add(s.skillId == LastUsedSkillId ? s.weight * 0.3f : s.weight);
             }
 
-            if (_weightedCandidates.Count == 0 || totalWeight <= 0f) return false;
-
-            // 加权随机抽取
-            float roll = UnityEngine.Random.Range(0f, totalWeight);
-            BossSkillSO selected = null;
-            float accum = 0f;
-            foreach (var (skill, w) in _weightedCandidates)
-            {
-                accum += w;
-                if (roll <= accum) { selected = skill; break; }
-            }
-            selected ??= _weightedCandidates[_weightedCandidates.Count - 1].skill;
+            // 加权随机抽取（共享原语：无正权重/无候选时返回 -1）
+            int idx = BaseGames.Core.WeightedPick.Index(_candidateWeights);
+            if (idx < 0) return false;
+            BossSkillSO selected = _weightedCandidates[idx];
 
             if (!CheckResourceCost(selected)) return false;