feat: demo显示听牌状态+可胡张数

引擎: MahjongRoom.GetTingTiles(player) 返回所有可胡的unique tile
Demo: 每回合后显示'听牌: X: 🀄听N张(tile1 tile2...) | Y: 未听...'
包含已胡/副露中的tile计数,兼容wildcard和258规则

示例: 听牌: AI-东: 🀄听 1张(中) | AI-南: 未听 | AI-西: 未听 | AI-北: 未听

RuleEngine/MahjongRoom.cs

@@ -892,4 +892,24 @@ public class MahjongRoom
         State.Phase = "settle";
         State.AddEvent("settle", "", null, "结算");
     }
+
+    /// <summary>返回玩家可胡牌的所有unique tile列表(听牌检测)。Empty=未听.</summary>
+    public List<int> GetTingTiles(string player)
+    {
+        var result = new List<int>();
+        bool require258 = _rules.WinCondition?.PairMustBe258 ?? false;
+        var allPossible = MahjongTile.AllTiles(_rules.Deck.IncludeHonors, false);
+        var hand = State.Hands[player];
+
+        foreach (var tile in allPossible)
+        {
+            int alreadyHave = hand.Count(t => t == tile);
+            if (alreadyHave >= 4) continue;
+            var checkHand = new List<int>(hand) { tile };
+            int wc = CountWildcardsInHand(checkHand);
+            var r = _solver.CheckWin(hand, newTile: tile, wildcardCount: wc, require258Pair: require258);
+            if (r != null && r.IsWin) result.Add(tile);
+        }
+        return result;
+    }
 }