feat: LockDetector — 残局锁手必胜序列检测

LockDetector.cs (新文件, 170行):
- BFS搜索: 手牌≤8张时寻找无人能压制的出牌序列
- 硬锁: 每步绝对无人可挡→跳过ISMCTS,直接走必胜路径
- 支持5种牌型: 炸弹/对子/三张/三带二/顺子/单张
- 利用CardTracker.CanAnyoneBeat()判断压制可能性
- 优先大牌型(炸弹>顺子>三带二>对子>单张)

IsmctsBot集成:
- DecidePlay开头: hand≤8→调用LockDetector
- 发现锁手→跳过ISMCTS模拟,直接出牌(Console打LOG)
- Type=CardType1.None交给引擎GetOutCard重新算

生效条件: 残局+CardTracker累积足够已知牌信息+手牌有压制力

PdkFriendServer/Logic/IsmctsBot.cs

@@ -82,7 +82,26 @@ namespace PdkFriendServer.Logic
                     {
                         _tracker.Update(view);
                         var hand = view.MyHand;
-                if (hand.Length == 0) return Pass(view);
+                        if (hand.Length == 0) return Pass(view);
+
+                        // 锁手检测：残局时跳过 ISMCTS，走必胜序列
+                        if (hand.Length <= 8)
+                        {
+                            var lockSeq = LockDetector.FindLockSequence(hand, _tracker, view.MyPos);
+                            if (lockSeq != null)
+                            {
+                                var firstPlay = lockSeq[0];
+                                Console.WriteLine($"[ISMCTS pos{view.MyPos}] LOCK {lockSeq.Count}步必胜 → 跳过模拟");
+                                // 通过引擎的出牌验证
+                            return new PlayOutCardPdkF
+                            {
+                                Pos = (byte)view.MyPos,
+                                GameNum = firstPlay.GameNum,
+                                Ids = firstPlay.Ids,
+                                Type = CardType1.None
+                            };
+                        }
+                    }
 
                 bool isFirstPlay = view.MaxPlayCard.GameNum <= 0;