fix: CheckWin守卫!=14拒绝副露后手牌 + FullHand合并副露

根因: CheckWin要求tiles.Count==14，碰/杠后手牌只有11/8/5/2张
修复:
- CheckWin守卫: !=14 → total%3!=2 (接受2,5,8,11,14)
- FullHand(): 合并手牌+Exposed副露→虚拟完整手牌
- 所有CheckWin调用点改用FullHand (MahjongRoom+PhaseMachine+HumanMahjongPlayer)
- 新增集成测试: 副露后11张手牌自摸

RuleEngine/Patterns/MeldsSolver.cs

@@ -27,7 +27,12 @@ public class MeldsSolver
     {
         var tiles = new List<int>(hand);
         if (newTile.HasValue) tiles.Add(newTile.Value);
-        if (tiles.Count + wildcardCount != 14) return new MeldsResult { IsWin = false };
+
+        // Standard mahjong hand: 4 melds (3 tiles each) + 1 pair (2 tiles) = 14 tiles
+        // With exposed melds, hand has fewer tiles. Valid counts: 2,5,8,11,14
+        int total = tiles.Count + wildcardCount;
+        if (total < 2 || total % 3 != 2 || total > 14)
+            return new MeldsResult { IsWin = false };
 
         tiles.Sort();