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/SkillUserSelectFilter.cs

@@ -0,0 +1,30 @@
+using System.Collections.Generic;
+
+public class SkillUserSelectFilter : ISkillSelectFilter
+{
+	public bool IsEmptyHanded;
+
+	private readonly string EMPTY_HANDED = "empty_handed";
+
+	private string _context = "";
+
+	public SkillUserSelectFilter(string value)
+	{
+		IsEmptyHanded = value == EMPTY_HANDED;
+		_context = value;
+		if (IsEmptyHanded)
+		{
+			_context = "1";
+		}
+	}
+
+	public int CalcCount(SkillOptionValue option)
+	{
+		return option.ParseInt(_context);
+	}
+
+	public IEnumerable<BattleCardBase> Filtering(IEnumerable<BattleCardBase> cards, SkillOptionValue option, SkillConditionCheckerOption checkerOption)
+	{
+		return cards;
+	}
+}