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.Tests/MahjongRoomIntegrationTests.cs

@@ -180,19 +180,21 @@ public class MahjongRoomIntegrationTests
 
     // === Constructed win scenario ===
     [Fact]
-    public void 构造听牌_庄家第一轮自摸()
+    public void 构造听牌_副露后自摸()
     {
         var rules = LoadDsl("xuezhandaodi");
         var room = new MahjongRoom(rules, new[] { "东", "南", "西", "北" });
         room.Deal();
 
-        // 东 has a complete win: 123万 456万 789万 111条 99条
-        room.State.Hands["东"] = new List<int> { 1,2,3,4,5,6,7,8,9,11,11,11,19,19 };
+        // 东 already pung-ed 1万: exposed has {1,1,1}
+        // Hand: 345万 888万 345条 88条 = 11 tiles → needs nothing, already winning
+        room.State.Hands["东"] = new List<int> { 3,4,5, 8,8,8, 13,14,15, 18,18 };
+        room.State.Exposed["东"] = new List<Meld> { new() { Type = "pung", Tiles = new() { 1,1,1 } } };
+        room.State.DiscardPool = new List<int>();
         room.State.Deck = new List<int>();
 
-        room.StepTurn(); // dealer first turn, no draw, checks win
+        room.StepTurn(); // dealer first turn, no draw, checks win with full hand
 
         Assert.Contains("东", room.State.HuPlayers);
-        Assert.True(room.State.AlivePlayers.Count < 4);
     }
 }