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/MotionUtils.cs

@@ -182,41 +182,6 @@ public class MotionUtils
 		return array;
 	}
 
-	public static Vector3[] GetCatmullRomSpline(Vector3[] p, int div, bool closed = false)
-	{
-		int num = p.Length;
-		List<Vector3> list = new List<Vector3>();
-		List<Vector3> list2 = new List<Vector3>();
-		if (closed)
-		{
-			list.Add(p[num - 1]);
-			list.AddRange(p);
-			list.Add(p[0]);
-			list.Add(p[1]);
-			num++;
-		}
-		else
-		{
-			list.Add(p[0]);
-			list.AddRange(p);
-			list.Add(p[num - 1]);
-		}
-		list2.Add(p[0]);
-		for (int i = 1; i < num; i++)
-		{
-			Vector3 vector = -1f * list[i - 1] + 3f * list[i] - 3f * list[i + 1] + 1f * list[i + 2];
-			Vector3 vector2 = 2f * list[i - 1] - 5f * list[i] + 4f * list[i + 1] - 1f * list[i + 2];
-			Vector3 vector3 = -1f * list[i - 1] + 0f * list[i] + 1f * list[i + 1] + 0f * list[i + 2];
-			Vector3 vector4 = 0f * list[i - 1] + 2f * list[i] + 0f * list[i + 1] + 0f * list[i + 2];
-			for (int j = 1; j <= div; j++)
-			{
-				float num2 = (float)j / (float)div;
-				list2.Add((vector * num2 * num2 * num2 + vector2 * num2 * num2 + vector3 * num2 + vector4) * 0.5f);
-			}
-		}
-		return list2.ToArray();
-	}
-
 	public static void SetLayerAll(GameObject obj, int layer)
 	{
 		obj.layer = layer;
@@ -269,33 +234,8 @@ public class MotionUtils
 		}
 	}
 
-	public static float GetAim(Vector2 p0, Vector2 p1)
-	{
-		float x = p1.x - p0.x;
-		return Mathf.Atan2(p1.y - p0.y, x) * 57.29578f - 90f;
-	}
-
-	public static Quaternion GetAimRotation(Vector3 p0, Vector3 p1)
-	{
-		return Quaternion.FromToRotation(Vector3.up, p1 - p0);
-	}
-
-	public static Vector2 GetPositionByAngle(float rot)
-	{
-		return new Vector2(Mathf.Cos(rot / 180f * (float)Math.PI), Mathf.Sin(rot / 180f * (float)Math.PI));
-	}
-
 	public static float CalculateFrameRateIndependantDampingConstant(float smoothingAmount, float decayMultiplier)
 	{
 		return 1f - Mathf.Pow(smoothingAmount, Time.smoothDeltaTime * decayMultiplier);
 	}
-
-	public static int GetDigit(int value)
-	{
-		if (value == 0)
-		{
-			return 1;
-		}
-		return (int)Mathf.Log10(Mathf.Abs(value)) + 1;
-	}
 }