cull(engine-cleanup): pass-8 phase-2 cascade round 4

[trim] fully-unreachable files deleted: 0
[trim] files edited: 5, files deleted: 0, nodes removed: 12
[type-trim] files edited: 0, types removed: 0

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

SVSim.BattleEngine/Shim/GodObjects/GodObjects.cs

@@ -65,7 +65,6 @@ public class GameMgr
     private GameObjMgr _gameObj = new GameObjMgr();
     private PrefabMgr _prefab;
     private InputMgr _input;
-    private BattleControl _battleCtrl;
     private NetworkUserInfoData _netUser;
 
     public EffectMgr GetEffectMgr() => _effect ??= new EffectMgr();