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/UIDragDropItem.cs

@@ -73,18 +73,6 @@ public class UIDragDropItem : MonoBehaviour
 		mCollider2D = base.gameObject.GetComponent<Collider2D>();
 	}
 
-	protected virtual void OnEnable()
-	{
-	}
-
-	protected virtual void OnDisable()
-	{
-		if (mDragging)
-		{
-			StopDragging(UICamera.hoveredObject);
-		}
-	}
-
 	protected virtual void Start()
 	{
 		mButton = GetComponent<UIButton>();
@@ -204,31 +192,6 @@ public class UIDragDropItem : MonoBehaviour
 	{
 	}
 
-	protected virtual void OnDrag(Vector2 delta)
-	{
-		if (interactable && mDragging && base.enabled && mTouch == UICamera.currentTouch)
-		{
-			OnDragDropMove(delta * mRoot.pixelSizeAdjustment);
-		}
-	}
-
-	protected virtual void OnDragEnd()
-	{
-		if (interactable && base.enabled && mTouch == UICamera.currentTouch)
-		{
-			StopDragging(UICamera.hoveredObject);
-		}
-	}
-
-	public void StopDragging(GameObject go)
-	{
-		if (mDragging)
-		{
-			mDragging = false;
-			OnDragDropRelease(go);
-		}
-	}
-
 	protected virtual void OnDragDropStart()
 	{
 		if (!draggedItems.Contains(this))
@@ -287,74 +250,4 @@ public class UIDragDropItem : MonoBehaviour
 	{
 		mTrans.localPosition += (Vector3)delta;
 	}
-
-	protected virtual void OnDragDropRelease(GameObject surface)
-	{
-		if (!cloneOnDrag)
-		{
-			if (mButton != null)
-			{
-				mButton.isEnabled = true;
-			}
-			else if (mCollider != null)
-			{
-				mCollider.enabled = true;
-			}
-			else if (mCollider2D != null)
-			{
-				mCollider2D.enabled = true;
-			}
-			UIDragDropContainer uIDragDropContainer = (surface ? NGUITools.FindInParents<UIDragDropContainer>(surface) : null);
-			if (uIDragDropContainer != null)
-			{
-				mTrans.parent = ((uIDragDropContainer.reparentTarget != null) ? uIDragDropContainer.reparentTarget : uIDragDropContainer.transform);
-				Vector3 localPosition = mTrans.localPosition;
-				localPosition.z = 0f;
-				mTrans.localPosition = localPosition;
-			}
-			else
-			{
-				mTrans.parent = mParent;
-			}
-			mParent = mTrans.parent;
-			mGrid = NGUITools.FindInParents<UIGrid>(mParent);
-			mTable = NGUITools.FindInParents<UITable>(mParent);
-			if (mDragScrollView != null)
-			{
-				StartCoroutine(EnableDragScrollView());
-			}
-			NGUITools.MarkParentAsChanged(base.gameObject);
-			if (mTable != null)
-			{
-				mTable.repositionNow = true;
-			}
-			if (!IsGridRepositionUse)
-			{
-				mGrid = null;
-			}
-			if (mGrid != null)
-			{
-				mGrid.repositionNow = true;
-			}
-		}
-		else
-		{
-			NGUITools.Destroy(base.gameObject);
-		}
-		OnDragDropEnd();
-	}
-
-	protected virtual void OnDragDropEnd()
-	{
-		draggedItems.Remove(this);
-	}
-
-	protected IEnumerator EnableDragScrollView()
-	{
-		yield return new WaitForEndOfFrame();
-		if (mDragScrollView != null)
-		{
-			mDragScrollView.enabled = true;
-		}
-	}
 }