feat(enemy): 选招器支持防重复折扣——WeightedRandomAntiRepeat

上一次选中的招按 EnemyStatsSO.attackAntiRepeatFactor 折扣权重（默认 0.3）。
折扣把唯一候选压到 0 时退化为 Priority 路径，不会出现敌人永不出手。
阶段切换清空防重复记忆。取代 BossBase.UseBossSkillWeighted 里的同名逻辑。

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

Assets/Tests/EditMode/Enemies/EnemyAttackSelectorTests.cs

@@ -104,5 +104,84 @@ namespace BaseGames.Tests.EditMode.Enemies
             for (int i = 0; i < 50; i++)
                 Assert.AreSame(ok, Sel(bad, ok).Select(true, true, AttackSelectionMode.WeightedRandom));
         }
+
+        // ── WeightedRandomAntiRepeat ─────────────────────────────────────────
+
+        static EnemyAttackSelector SelAntiRepeat(float factor, params IAttackCandidate[] cs)
+            => new EnemyAttackSelector(new List<IAttackCandidate>(cs), factor);
+
+        [Test]
+        public void AntiRepeat_ZeroFactor_NeverPicksSameTwiceWhenAlternativeExists()
+        {
+            var a = new FakeCandidate { WeightV = 1f };
+            var b = new FakeCandidate { WeightV = 1f };
+            var s = SelAntiRepeat(0f, a, b);
+
+            var prev = s.Select(true, true, AttackSelectionMode.WeightedRandomAntiRepeat);
+            for (int i = 0; i < 100; i++)
+            {
+                var cur = s.Select(true, true, AttackSelectionMode.WeightedRandomAntiRepeat);
+                Assert.AreNotSame(prev, cur, "系数为 0 时不应连续选中同一招");
+                prev = cur;
+            }
+        }
+
+        [Test]
+        public void AntiRepeat_ZeroFactor_SingleCandidate_StillReturnsIt()
+        {
+            // 只有一招时折扣会把权重压到 0，WeightedPick 返回 -1；
+            // 必须退化为 Priority 路径把它选出来，否则敌人永远不出手。
+            var only = new FakeCandidate { WeightV = 1f };
+            var s = SelAntiRepeat(0f, only);
+
+            for (int i = 0; i < 10; i++)
+                Assert.AreSame(only, s.Select(true, true, AttackSelectionMode.WeightedRandomAntiRepeat));
+        }
+
+        [Test]
+        public void AntiRepeat_DiscountsPreviousPick_ButDoesNotBanIt()
+        {
+            // 系数 0.5：a 被选过后权重折半，但仍有机会再被选中。
+            var a = new FakeCandidate { WeightV = 1f };
+            var b = new FakeCandidate { WeightV = 1f };
+            var s = SelAntiRepeat(0.5f, a, b);
+
+            s.Select(true, true, AttackSelectionMode.WeightedRandomAntiRepeat);
+            int repeats = 0;
+            var prev = s.LastPicked;
+            for (int i = 0; i < 400; i++)
+            {
+                var cur = s.Select(true, true, AttackSelectionMode.WeightedRandomAntiRepeat);
+                if (ReferenceEquals(cur, prev)) repeats++;
+                prev = cur;
+            }
+            Assert.Greater(repeats, 0,   "折扣不应等于禁用");
+            Assert.Less   (repeats, 200, "折扣后重复率应低于无折扣时的约 50%");
+        }
+
+        [Test]
+        public void AntiRepeat_IneligiblePrevious_DoesNotBlockOthers()
+        {
+            var a = new FakeCandidate { WeightV = 1f };
+            var b = new FakeCandidate { WeightV = 1f };
+            var s = SelAntiRepeat(0f, a, b);
+
+            var first = s.Select(true, true, AttackSelectionMode.WeightedRandomAntiRepeat);
+            ((FakeCandidate)first).CanUseV = false;    // 上一招进冷却
+
+            var second = s.Select(true, true, AttackSelectionMode.WeightedRandomAntiRepeat);
+            Assert.IsNotNull(second);
+            Assert.AreNotSame(first, second);
+        }
+
+        [Test]
+        public void PlainWeighted_DoesNotApplyAntiRepeat()
+        {
+            // WeightedRandom 模式下唯一候选恒被选中（回归：折扣不得泄漏到旧模式）
+            var only = new FakeCandidate { WeightV = 1f };
+            var s = SelAntiRepeat(0f, only);
+            for (int i = 0; i < 10; i++)
+                Assert.AreSame(only, s.Select(true, true, AttackSelectionMode.WeightedRandom));
+        }
     }
 }

Assets/_Game/Scripts/Enemies/Abilities/AttackSelectionMode.cs

@@ -3,7 +3,8 @@ namespace BaseGames.Enemies.Abilities
     /// <summary>多攻击选招策略。</summary>
     public enum AttackSelectionMode
     {
-        WeightedRandom, // 合格集内按 weight 加权随机
-        Priority        // 合格集内取 priority 最高（并列取首个）
+        WeightedRandom,           // 合格集内按 weight 加权随机
+        Priority,                 // 合格集内取 priority 最高（并列取首个）
+        WeightedRandomAntiRepeat, // 同 WeightedRandom，但对上一次选中的招施加权重折扣，压低连续重复
     }
 }

Assets/_Game/Scripts/Enemies/Abilities/EnemyAttackSelector.cs

@@ -12,15 +12,26 @@ namespace BaseGames.Enemies.Abilities
         private readonly List<IAttackCandidate> _candidates;
         // 权重缓冲区（与 _candidates 等长，每次选招复用）：避免每次选招 new List 造成 GC
         private readonly List<float> _weightBuf;
+        // 防重复折扣系数：0 = 有替代时绝不连续重复，1 = 不惩罚
+        private readonly float _antiRepeatFactor;
 
-        public EnemyAttackSelector(IEnumerable<IAttackCandidate> candidates)
+        private IAttackCandidate _lastPicked;
+
+        public EnemyAttackSelector(IEnumerable<IAttackCandidate> candidates, float antiRepeatFactor = 0.3f)
         {
-            _candidates = new List<IAttackCandidate>(candidates);
-            _weightBuf  = new List<float>(_candidates.Count);
+            _candidates       = new List<IAttackCandidate>(candidates);
+            _weightBuf        = new List<float>(_candidates.Count);
+            _antiRepeatFactor = Mathf.Clamp01(antiRepeatFactor);
         }
 
         public int Count => _candidates.Count;
 
+        /// <summary>上一次实际选中的招（防重复折扣的作用对象；供测试与调试面板读取）。</summary>
+        public IAttackCandidate LastPicked => _lastPicked;
+
+        /// <summary>对象池复用 / 阶段切换时清除防重复记忆。</summary>
+        public void ResetRepeatMemory() => _lastPicked = null;
+
         private static bool Eligible(IAttackCandidate c, bool hasLOS, bool grounded)
             => c != null && c.CanUse && c.InAttackRange()
                && (!c.RequiresLineOfSight || hasLOS)
@@ -34,9 +45,24 @@ namespace BaseGames.Enemies.Abilities
         }
 
         public IAttackCandidate Select(bool hasLOS, bool grounded, AttackSelectionMode mode)
-            => mode == AttackSelectionMode.Priority
-                ? SelectByPriority(hasLOS, grounded)
-                : SelectByWeight(hasLOS, grounded);
+        {
+            switch (mode)
+            {
+                case AttackSelectionMode.Priority:
+                    return Remember(SelectByPriority(hasLOS, grounded));
+                case AttackSelectionMode.WeightedRandomAntiRepeat:
+                    return Remember(SelectByWeight(hasLOS, grounded, antiRepeat: true));
+                default:
+                    return Remember(SelectByWeight(hasLOS, grounded, antiRepeat: false));
+            }
+        }
+
+        // 只在真选中了东西时更新记忆：选空时保留上一招，避免"空一帧就清掉防重复"。
+        private IAttackCandidate Remember(IAttackCandidate pick)
+        {
+            if (pick != null) _lastPicked = pick;
+            return pick;
+        }
 
         private IAttackCandidate SelectByPriority(bool hasLOS, bool grounded)
         {
@@ -50,20 +76,25 @@ namespace BaseGames.Enemies.Abilities
             return best;
         }
 
-        private IAttackCandidate SelectByWeight(bool hasLOS, bool grounded)
+        private IAttackCandidate SelectByWeight(bool hasLOS, bool grounded, bool antiRepeat)
         {
             // 有效权重：不合格候选填 0（由共享原语保证零权重项绝不被选中）。缓冲区复用 → 选招零 GC。
             _weightBuf.Clear();
             for (int i = 0; i < _candidates.Count; i++)
             {
                 var c = _candidates[i];
-                _weightBuf.Add(Eligible(c, hasLOS, grounded) ? Mathf.Max(0f, c.Weight) : 0f);
+                float w = Eligible(c, hasLOS, grounded) ? Mathf.Max(0f, c.Weight) : 0f;
+                // 防重复：上一招权重打折。折扣可把权重压到 0——此时若它是唯一候选，
+                // 下面的 Priority 退化路径会把它选出来，不会出现"敌人永远不出手"。
+                if (antiRepeat && w > 0f && ReferenceEquals(c, _lastPicked))
+                    w *= _antiRepeatFactor;
+                _weightBuf.Add(w);
             }
 
             int idx = BaseGames.Core.WeightedPick.Index(_weightBuf);
             if (idx >= 0) return _candidates[idx];
 
-            // 无正权重（合格候选权重全 0）→ 退化为按 Priority 选(并列取首个)
+            // 无正权重（合格候选权重全 0，或全被防重复折扣压平）→ 退化为按 Priority 选(并列取首个)
             return SelectByPriority(hasLOS, grounded);
         }
     }

Assets/_Game/Scripts/Enemies/Boss/BossBase.cs

@@ -184,6 +184,8 @@ namespace BaseGames.Enemies
 
             _currentPhase       = phase;
             LastUsedSkillId     = null;  // 新阶段重置权重惩罚，防止跨阶段漂移
+            // 新阶段换招池，上一阶段的防重复记忆不应跨阶段影响选招
+            AttackSelector?.ResetRepeatMemory();
             _onBossPhaseChanged?.Raise(new BossPhaseEvent
             {
                 BossId = _bossId,

Assets/_Game/Scripts/Enemies/EnemyBase.cs

@@ -601,7 +601,10 @@ namespace BaseGames.Enemies
                     candidates.Add(ab);
                 }
             }
-            _attackSelector = new Abilities.EnemyAttackSelector(candidates);
+            // 折扣系数是策划配置项，未配 StatsSO 的敌人用 0.3 这个合法业务缺省（非掩盖漏配：
+            // 该模式本身是可选的，没配就等于用默认折扣）。
+            float antiRepeat = _statsSO != null ? _statsSO.attackAntiRepeatFactor : 0.3f;
+            _attackSelector = new Abilities.EnemyAttackSelector(candidates, antiRepeat);
         }
 
         protected virtual void Update()

Assets/_Game/Scripts/Enemies/EnemyStatsSO.cs

@@ -44,6 +44,10 @@ namespace BaseGames.Enemies
         public BaseGames.Enemies.Abilities.AttackSelectionMode attackSelectionMode
             = BaseGames.Enemies.Abilities.AttackSelectionMode.WeightedRandom;
 
+        [Tooltip("WeightedRandomAntiRepeat 模式下，上一次选中的招的权重折扣系数。" +
+                 "0 = 有替代招时绝不连续重复；1 = 不惩罚。仅该模式生效")]
+        [Range(0f, 1f)] public float attackAntiRepeatFactor = 0.3f;
+
         [Header("追击 & AI 阶段")]
         [Tooltip("是否有警觉状态：勾选=未发现态进入视野先进警觉(朝向+警觉动画)再追击；不勾选=进入追逐感知直接追击")]
         public bool HasAlertState = true;