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/Shim/View/VfxShim.cs

@@ -16,12 +16,9 @@ namespace Wizard.Battle.View.Vfx
     public class VfxBase
     {
         public virtual bool IsEnd { get; protected set; } = true;
-        public virtual string CurrentVfxName => GetType().ToString();
         public virtual void Update(float dt, List<IEffectVfx> effectVfxList) { }
         public virtual void Play() { }
-        public virtual VfxBase Cancel() => this;
         public virtual bool IsVfxNonEmpty() => false;
-        public virtual List<string> GetVfxNames() => new List<string>();
     }
 
     public sealed class NullVfx : VfxBase
@@ -62,8 +59,6 @@ namespace Wizard.Battle.View.Vfx
         public static SequentialVfxPlayer Create(params VfxBase[] vfxCollection)
         { var p = new SequentialVfxPlayer(); if (vfxCollection != null) p._children.AddRange(vfxCollection); return p; }
         public void Register(VfxBase vfx) { if (vfx != null) _children.Add(vfx); }
-        public int Count() => _children.Count;
-        public List<VfxBase> GetAllVfxAsList() => new List<VfxBase>(_children);
         public override bool IsVfxNonEmpty()
         {
             foreach (var c in _children) { if (c != null && c.IsVfxNonEmpty()) return true; }
@@ -124,32 +119,19 @@ namespace Wizard.Battle.View.Vfx
         public VfxWith(VfxBase vfx, T1 value1, T2 value2) { Vfx = vfx; Value_1 = value1; Value_2 = value2; }
     }
 
-    // m1_stub_gen drops `event` decls (session-6 gap) — re-add StartSkillSelectVfx.OnStart
-    // that its generated stub lost. Re-check this if CS1061 on an event name recurs.
-    public partial class StartSkillSelectVfx { public event System.Action OnStart; }
-
     public class EvolveVfxBase : VfxBase { }
-    public partial class CanNotTouchCardVfx : VfxBase { }
 
-    public partial interface ICardVfxCreator { }
-    public interface IBattleCardVfxCreator { }
 
     // The VFX manager: headless, registration is suppressed (real VfxMgr early-returns
     // when IsForecast; we no-op unconditionally since we never pump the render loop).
     public class VfxMgr
     {
         public virtual bool IsEnd => true;
-        public string CurrentVfxName => "";
-        public int CurrentVfxTime => 0;
         public void RegisterImmediateVfx<T>(T vfx) where T : VfxBase { }
-        public void Register<T>(T vfx) where T : VfxBase { }
         public virtual void RegisterSequentialVfx<T>(T vfx) where T : VfxBase { }
-        public Queue<VfxBase> GetSequentialVfxQueues() => new Queue<VfxBase>();
         public List<VfxBase> GetVfxList<TType>() => new List<VfxBase>();
-        public static void CheckAndAddEffectVfxList(VfxBase vfx, List<IEffectVfx> effectVfxList) { }
         public virtual void Update(float dt) { }
         public virtual void Cancel() { }
         public void Dispose() { }
-        public void Clear() { }
     }
 }