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/BetterList.cs

@@ -23,22 +23,6 @@ public class BetterList<T>
 		}
 	}
 
-	[DebuggerHidden]
-	[DebuggerStepThrough]
-	public IEnumerator<T> GetEnumerator()
-	{
-		if (buffer != null)
-		{
-			int i = 0;
-			while (i < size)
-			{
-				yield return buffer[i];
-				int num = i + 1;
-				i = num;
-			}
-		}
-	}
-
 	private void AllocateMore()
 	{
 		T[] array = ((buffer != null) ? new T[Mathf.Max(buffer.Length << 1, 32)] : new T[32]);
@@ -74,12 +58,6 @@ public class BetterList<T>
 		size = 0;
 	}
 
-	public void Release()
-	{
-		size = 0;
-		buffer = null;
-	}
-
 	public void Add(T item)
 	{
 		if (buffer == null || size == buffer.Length)
@@ -89,63 +67,6 @@ public class BetterList<T>
 		buffer[size++] = item;
 	}
 
-	public void Insert(int index, T item)
-	{
-		if (buffer == null || size == buffer.Length)
-		{
-			AllocateMore();
-		}
-		if (index > -1 && index < size)
-		{
-			for (int num = size; num > index; num--)
-			{
-				buffer[num] = buffer[num - 1];
-			}
-			buffer[index] = item;
-			size++;
-		}
-		else
-		{
-			Add(item);
-		}
-	}
-
-	public bool Contains(T item)
-	{
-		if (buffer == null)
-		{
-			return false;
-		}
-		for (int i = 0; i < size; i++)
-		{
-			ref readonly T reference = ref buffer[i];
-			object obj = item;
-			if (reference.Equals(obj))
-			{
-				return true;
-			}
-		}
-		return false;
-	}
-
-	public int IndexOf(T item)
-	{
-		if (buffer == null)
-		{
-			return -1;
-		}
-		for (int i = 0; i < size; i++)
-		{
-			ref readonly T reference = ref buffer[i];
-			object obj = item;
-			if (reference.Equals(obj))
-			{
-				return i;
-			}
-		}
-		return -1;
-	}
-
 	public bool Remove(T item)
 	{
 		if (buffer != null)
@@ -199,31 +120,4 @@ public class BetterList<T>
 		Trim();
 		return buffer;
 	}
-
-	[DebuggerHidden]
-	[DebuggerStepThrough]
-	public void Sort(CompareFunc comparer)
-	{
-		int num = 0;
-		int num2 = size - 1;
-		bool flag = true;
-		while (flag)
-		{
-			flag = false;
-			for (int i = num; i < num2; i++)
-			{
-				if (comparer(buffer[i], buffer[i + 1]) > 0)
-				{
-					T val = buffer[i];
-					buffer[i] = buffer[i + 1];
-					buffer[i + 1] = val;
-					flag = true;
-				}
-				else if (!flag)
-				{
-					num = ((i != 0) ? (i - 1) : 0);
-				}
-			}
-		}
-	}
 }