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/GodObjects/ClosureStubs.cs

@@ -1,38 +1,16 @@
-// Empty type stubs to satisfy references from full-surface generated god-object stubs.
-// Each is referenced only as a type in a no-op signature; members (if any) surface in a
-// later frontier wave and can be filled by m1_stub_gen --type <Name>.
-public partial class FadeManager { }
-public partial class FriendBase { }
-public partial class RoomDialog { }
-public partial class VideoHostingHUDFaceCamera { }
 
 namespace Wizard
 {
-    public partial class ConventionRoomBattleWatchTask { }
-    public partial class OpenRoomBattleGetRecoveryParamTask { }
-    public partial class ScenarioOption { }
-    public partial class AppleLogin { public partial class Error { } }
-    public partial class ScenarioTemporaryVoice { public partial class DownloadInfo { } }
 }
 
 namespace Wizard.RoomMatch
 {
-    public partial class PlayerController { public Player Target { get; } }
     public partial class RoomBase { }
-    public partial class RoomFormatEventHandler { }
-    public partial class RoomWatchEventDispatch { }
     public partial class RoomRoot : global::UIBase { public void CreateChangeSceneDialog(UIManager.ViewScene nextScene, UIManager.ChangeViewSceneParam param = null, System.Action moveCallBack = null) { } }
-    public partial class RoomConnectChecker { }
-    public partial class RoomVisitor { }
-    public partial class RoomInviteFriend { }
-    public partial class RoomFirstTurnSelect { }
-    public partial class RoomDeckList { }
-    public partial class RoomCommonEventHandler { }
 }
 
 namespace Wizard.UIFriend
 {
-    public partial class RoomFriendTask { }
 }
 
 namespace Wizard.UI.Common
@@ -42,26 +20,20 @@ namespace Wizard.UI.Common
 
 namespace Wizard.UI.Dialog.ImageSelection
 {
-    public partial class ImageSelectionBaseUI { }
 }
 
 namespace Wizard.Battle.UI
 {
-    public partial class BattleLogButton { }
-    public partial class BattleLogItemSet { }
 }
 
 namespace Wizard.UI.ReportToManagement
 {
-    public partial class DialogReportToManagement { public static DialogBase Create(long battleId = -1L) => default!; }
 }
 
 namespace Wizard.Dialog.Setting
 {
-    public partial class SettingFirstBattle { }
 }
 
 namespace Cute
 {
-    public partial class UpdateSocialAccountTask { }
 }