cull(engine-cleanup): pass-8 phase-2 cascade round 1

[trim] fully-unreachable files deleted: 6
[trim] files edited: 55, files deleted: 0, nodes removed: 244
[type-trim] files edited: 1, types removed: 1

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

SVSim.BattleEngine/Engine/RoomTwoPickBeforeBattleInfo.cs

@@ -10,9 +10,4 @@ public class RoomTwoPickBeforeBattleInfo
 		receiveDeck = new Deck();
 		receiveDeck.cardIds = new int[0];
 	}
-
-	public void ReceiveBackDraftCharaId(int id)
-	{
-		receiveDeck.skinId = id;
-	}
 }