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.Tests/Coverage/CoverageRecorder.cs

@@ -0,0 +1,72 @@
+extern alias engine;
+using System.Collections.Concurrent;
+using System.IO;
+using System.Linq;
+using System.Reflection;
+using HarmonyLib;
+
+namespace SVSim.BattleEngine.Tests.Coverage;
+
+/// <summary>Harmony-prefix-based method-invocation logger over SVSim.BattleEngine.dll.
+/// Idempotent: Install is safe to call from every fixture's [OneTimeSetUp]; only the first
+/// call patches.</summary>
+public static class CoverageRecorder
+{
+    private static readonly ConcurrentDictionary<string, byte> _hit = new();
+    private static readonly Harmony _h = new("svsim.engine.coverage");
+    private static bool _installed;
+    private static readonly object _gate = new();
+
+    public static int HitCount => _hit.Count;
+
+    public static void Reset() => _hit.Clear();
+
+    public static void Install()
+    {
+        lock (_gate)
+        {
+            if (_installed) return;
+            _installed = true;
+        }
+
+        var asm = typeof(engine::BattleManagerBase).Assembly;
+        var prefix = AccessTools.Method(typeof(CoverageRecorder), nameof(Hit));
+        var hm = new HarmonyMethod(prefix);
+
+        foreach (var t in asm.GetTypes())
+        {
+            var ns = t.FullName ?? string.Empty;
+            // Only engine + shim types — skip framework/3rd-party that happens to be co-located.
+            if (!ns.StartsWith("SVSim.BattleEngine.") &&
+                !ns.StartsWith("Wizard.") &&
+                !ns.StartsWith("Cute.") &&
+                !ns.StartsWith("Toolbox.") &&
+                !ns.StartsWith("UnityEngine.")) continue;
+            if (t.IsGenericTypeDefinition) continue;
+
+            var members = t.GetMethods(BindingFlags.Instance | BindingFlags.Static |
+                                       BindingFlags.Public   | BindingFlags.NonPublic |
+                                       BindingFlags.DeclaredOnly);
+            foreach (var m in members)
+            {
+                if (m.IsAbstract) continue;
+                if (m.ContainsGenericParameters) continue;
+                if (m.GetMethodBody() is null) continue;
+                try { _h.Patch(m, prefix: hm); } catch { /* generic/inlined; skipped */ }
+            }
+        }
+    }
+
+    public static void Dump(string path)
+    {
+        Directory.CreateDirectory(Path.GetDirectoryName(path)!);
+        File.WriteAllLines(path, _hit.Keys.OrderBy(k => k));
+    }
+
+    private static void Hit(MethodBase __originalMethod)
+    {
+        var t = __originalMethod.DeclaringType;
+        if (t is null) return;
+        _hit.TryAdd($"{t.FullName}.{__originalMethod.Name}", 0);
+    }
+}