feat(battle-engine): full Unity/VFX/god-object shims + expanded copy closure (2570 files)

Authored Unity primitive/object-model shim, VFX layer (control-flow-preserving, InstantVfx never invokes its action -- headless suppression), god-object stubs (GameMgr/EffectMgr/UIManager with faithfully-extracted nested enums), View/UI/Touch tree, LitJson+BetterList+Tuple copied, third-party stubs. Discovered Roslyn header-error masking: fixing class-header type errors unmasks body references, so the true copy closure is ~2570 files (was 782 under masking). Errors: masked-25720 -> 268; our shim files compile clean. Remaining: ~50 residual shim/external types, 24 NGUI UI-base overrides, static-type fixes, plus likely 1-2 more unmask waves.

SVSim.BattleEngine/Engine/SkillSelectIndexFilter.cs

@@ -0,0 +1,32 @@
+using System.Collections.Generic;
+using System.Linq;
+
+public class SkillSelectIndexFilter : ISkillSelectFilter
+{
+	private readonly int _index;
+
+	public SkillSelectIndexFilter(int index)
+	{
+		_index = index;
+	}
+
+	public int CalcCount(SkillOptionValue option)
+	{
+		return 1;
+	}
+
+	public IEnumerable<BattleCardBase> Filtering(IEnumerable<BattleCardBase> cards, SkillOptionValue option, SkillConditionCheckerOption checkerOption)
+	{
+		IEnumerable<BattleCardBase> result = new BattleCardBase[0];
+		if (checkerOption.SelectedCards == null || checkerOption.SelectedCards.Count == 0)
+		{
+			return result;
+		}
+		BattleCardBase selectCard = checkerOption.SelectedCards[_index].SelectCard;
+		if (cards.Contains(selectCard))
+		{
+			result = new BattleCardBase[1] { selectCard };
+		}
+		return result;
+	}
+}