engine cleanup passes 4-7 + multi-instancing ambient rip

Squashes 146 commits from battle-engine-extraction. Net: 2,045 files changed,
+11,896 / -158,687 lines. Ships engine passes 4-7 (dead-code cull, view-layer
stub, receive-path shrink) plus the Phase-5 AsyncLocal ambient deletion that
turns concurrent battles into a type-system property rather than a scope
contract.

## What landed

**Passes 4-7 (chunks 1-34):** Extended the Phase-4 const-false collapse into a
cascading cull across the skill graph, view layer, and receive-path periphery.
Six mode flags (IsWatchBattle/IsReplayBattle/IsAdmin/IsAdminWatch/IsPuzzleQuest/
IsAINetwork) became `const false`, every guarded block deleted. Field*.cs
subclass ctors + BackGroundBase + ObjectChecker culled to no-ops. Mulligan
family reworked to take a mgr param through IMulliganMgr.InitMulligan.
Emotion/Recovery/Resource clusters null-stubbed. Prediction/OperationSimulator/
skill filters converted from static ambient reads to per-mgr reads via
SkillPrm.ownerCard.SelfBattlePlayer.BattleMgr / ins.BattleMgr / this.BattleMgr.

**Phase-5 ambient rip (chunks 35-47):** Deleted BattleAmbient / BattleAmbient-
Context / TestBattleScope in full. Every per-battle mutable slot now lives on
the mgr instance itself:
  mgr.InstanceIsForecast / InstanceIsRandomDraw / InstanceRecoveryInfo /
  InstanceViewerId / InstanceNetworkAgent / GameMgr
BattleManagerBase.GetIns() returns null unconditionally; the residual static
flags + 3 façades (Certification.ViewerId, Data.BattleRecoveryInfo,
ToolboxGame.RealTimeNetworkAgent) are null-tolerant defaults kept for the
handful of engine-internal readers that still reference their types. Zero
BattleAmbient references anywhere in engine + node + tests.

Added pre-seeded GameMgr ctor overload threaded through the mgr chain
(BattleManagerBase → SingleBattleMgr / NetworkBattleManagerBase → NetworkStandard-
BattleMgr → HeadlessBattleMgr / HeadlessNetworkBattleMgr). Fixtures build a
GameMgr, seed it via HeadlessEngineEnv.SeedCharaIds/SeedNetUser, and pass it
to the mgr's ctor — no ambient reach.

Node side (SVSim.BattleNode/SessionBattleEngine): _ctx replaced with a plain
GameMgr field; 34 `using var _ambient = BattleAmbient.Enter(_ctx)` scope wraps
ripped from every accessor and mutator; EngineGlobalInit.WirePerSessionGameMgr
takes GameMgr as a param and runs from SessionBattleEngine.SetupInternal
BEFORE mgr construction.

Test side: TestBattleScope deleted; 18 fixture [SetUp]s migrated to
`HeadlessEngineEnv.EnsureProcessGlobals()`; MultiInstanceEngineTests rewritten
around per-mgr construction (GetIns() → null is the pinned invariant).

## Regression fixes

- **chunk-48** (MulliganCtrl): chunk-35's `= null` stubs on card lookups broke
  the live receive-driven Deal path (BattlePlayerBase.DrawCard NRE'd downstream
  of NetworkPlayerMulliganCtrl.StartMulliganVfx). Restored the three lookups
  via `_battlePlayer.BattleMgr.GetBattleCardIdx`. Engine tests were satisfied
  by the WireMulliganPhase seam; unit tests exposed the live-path gap.

## Ship state

- SVSim.BattleEngine.Tests: 56/56 pass, 2 skip
- SVSim.UnitTests: 1554/1554 pass (was 1523/31-fail before chunk 48)
- Solution build: 0 source warnings (40 pre-existing NU1902 MessagePack CVEs
  in SVSim.EmulatedEntrypoint, unrelated)
- Sequential PVP smoke: verified live (two back-to-back battles, no regression
  on cleanup/spinup)
- Concurrent PVP smoke: verified live

Adds tools/engine-port/ClosureAnalyzer/ — the Roslyn transitive-type-closure
analyzer needed to make future cascade cleanup safe (per feedback memory
"Engine cleanup needs closure tool" from the 2026-06-28 pass-3 failure).

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

SVSim.BattleEngine/Engine/Skill_cost_change.cs

@@ -19,16 +19,6 @@ public class Skill_cost_change : SkillBase
 		}
 	}
 
-	private const string EACH_TARGET_OPTION = "each_target";
-
-	public const string HALF_COST_PARAMETER_ROUND_UP = "half";
-
-	public const string HALF_COST_PARAMETER_ROUND_DOWN = "half_round_down";
-
-	public const int SET_COST_DEFAULT_INT = int.MinValue;
-
-	public const int ADD_COST_DEFAULT_INT = int.MinValue;
-
 	protected int _addValue = int.MinValue;
 
 	protected int _setValue = int.MinValue;
@@ -135,7 +125,7 @@ public class Skill_cost_change : SkillBase
 				}
 			}
 		}
-		CostChangeVfx costChangeVfx = new CostChangeVfx(_targets, OnWhenSpellChargeStart != 0, _isCostUpList, isStop: false);
+		VfxWithLoadingSequential costChangeVfx = VfxWithLoadingSequential.Create();
 		parallelVfxPlayer.Register(costChangeVfx.MainVfx);
 		if (OnAccumulationCostChange != null && !HasEachTargetOption())
 		{
@@ -253,7 +243,7 @@ public class Skill_cost_change : SkillBase
 		}
 		buffInfoContainer.Clear();
 		StopEnd(skillProcessor);
-		return VfxWithLoading.Create(new CostChangeVfx(list, OnWhenSpellChargeStart != 0, new List<bool>(), isStop: true).MainVfx);
+		return VfxWithLoading.Create(VfxWithLoadingSequential.Create().MainVfx);
 	}
 
 	protected bool IsHalfRoundUpCostSkill(SkillFilterCreator.ContentKeyword nameType)
@@ -274,13 +264,6 @@ public class Skill_cost_change : SkillBase
 		return false;
 	}
 
-	public bool IsHalfCostSkill()
-	{
-		bool num = IsHalfRoundUpCostSkill(SkillFilterCreator.ContentKeyword.set);
-		bool flag = IsHalfRoundUpCostSkill(SkillFilterCreator.ContentKeyword.add);
-		return num || flag;
-	}
-
 	protected bool HasEachTargetOption()
 	{
 		return base.OptionValue.GetString(SkillFilterCreator.ContentKeyword.type, "NONE") == "each_target";
@@ -328,11 +311,11 @@ public class Skill_cost_change : SkillBase
 		{
 		case SkillProcessor.ProcessCallType.Start:
 		{
-			if ((!GameMgr.GetIns().IsAdminWatch && !base.SkillPrm.ownerCard.IsPlayer && !(base.ApplyingTargetFilter is SkillTargetSelfFilter) && !(base.ApplyingTargetFilter is SkillTargetHandSelfFilter) && base.SkillPrm.ownerCard.SelfBattlePlayer.HandCardList.Count > 0) || base.PreprocessList.Any((SkillPreprocessBase p) => p is SkillPreprocessOpenCard))
+			if ((!SkillPrm.ownerCard.SelfBattlePlayer.BattleMgr.GameMgr.IsAdminWatch && !base.SkillPrm.ownerCard.IsPlayer && !(base.ApplyingTargetFilter is SkillTargetSelfFilter) && !(base.ApplyingTargetFilter is SkillTargetHandSelfFilter) && base.SkillPrm.ownerCard.SelfBattlePlayer.HandCardList.Count > 0) || base.PreprocessList.Any((SkillPreprocessBase p) => p is SkillPreprocessOpenCard))
 			{
 				return true;
 			}
-			if (!base.SkillPrm.ownerCard.IsPlayer && !GameMgr.GetIns().IsAdminWatch)
+			if (!base.SkillPrm.ownerCard.IsPlayer && !SkillPrm.ownerCard.SelfBattlePlayer.BattleMgr.GameMgr.IsAdminWatch)
 			{
 				break;
 			}
@@ -345,11 +328,11 @@ public class Skill_cost_change : SkillBase
 			return false;
 		}
 		case SkillProcessor.ProcessCallType.ResidentStop:
-			if (!base.SkillPrm.ownerCard.IsPlayer && base.SkillPrm.ownerCard.IsInHand && !GameMgr.GetIns().IsAdminWatch)
+			if (!base.SkillPrm.ownerCard.IsPlayer && base.SkillPrm.ownerCard.IsInHand && !SkillPrm.ownerCard.SelfBattlePlayer.BattleMgr.GameMgr.IsAdminWatch)
 			{
 				return false;
 			}
-			if (base.SkillPrm.ownerCard.IsPlayer || GameMgr.GetIns().IsAdminWatch)
+			if (base.SkillPrm.ownerCard.IsPlayer || SkillPrm.ownerCard.SelfBattlePlayer.BattleMgr.GameMgr.IsAdminWatch)
 			{
 				return true;
 			}