feat(battle-engine): clear header frontier (Item/ErrorDialog/SDK shims + infra copies)

Resolves the 268-error header frontier: settings Item base, ErrorDialog.Data,
RoomConnectController nested types, Unity asset/light/collider types, CriWare/
CodeStage/Spine SDK surface, and copies INetworkLogger + SingletonMonoBehaviour
verbatim. Per F3 this unmasks the type bodies (~26.5k member-level errors now
visible) -- the real M1 bulk, attacked in following waves.

SVSim.BattleEngine/Shim/UnityEngine/UnityShim2.cs

@@ -0,0 +1,68 @@
+// AUTHORED SHIM (not copied). Second UnityEngine batch surfaced by the M1 compile
+// loop (wave after the 2,570-file copy closure). Same rules as UnityShim.cs: no-op
+// presentation/IO surface; add only what the compiler demands. Asset/light/collider
+// types are referenced only as field/parameter types or via suppressed-IO calls.
+using System;
+
+namespace UnityEngine
+{
+    public class TextAsset : Object
+    {
+        public string text => "";
+        public byte[] bytes => new byte[0];
+    }
+
+    public class AsyncOperation
+    {
+        public bool isDone => true;
+        public float progress => 1f;
+        public int priority { get; set; }
+        public bool allowSceneActivation { get; set; }
+    }
+
+    public class AssetBundle : Object
+    {
+        public static AssetBundle LoadFromFile(string path) => null;
+        public static AssetBundleCreateRequest LoadFromFileAsync(string path) => null;
+        public string[] GetAllAssetNames() => new string[0];
+        public T LoadAsset<T>(string name) where T : Object => null;
+        public Object LoadAsset(string name) => null;
+        public Object[] LoadAllAssets() => new Object[0];
+        public AssetBundleRequest LoadAllAssetsAsync() => null;
+        public void Unload(bool unloadAllLoadedObjects) { }
+    }
+
+    public class AssetBundleCreateRequest : AsyncOperation { public AssetBundle assetBundle => null; }
+    public class AssetBundleRequest : AsyncOperation { public Object asset => null; public Object[] allAssets => new Object[0]; }
+
+    public class Collider2D : Component { public bool enabled { get; set; } }
+    public class BoxCollider2D : Collider2D { }
+    public class Light : Behaviour { }
+    public class AudioListener : Behaviour { }
+
+    public enum RenderTextureFormat { ARGB32, Depth, ARGBHalf, ARGB64, Default }
+
+    public enum RuntimeInitializeLoadType
+    {
+        AfterSceneLoad, BeforeSceneLoad, AfterAssembliesLoaded,
+        BeforeSplashScreen, SubsystemRegistration
+    }
+
+    public sealed class RuntimeInitializeOnLoadMethodAttribute : Attribute
+    {
+        public RuntimeInitializeOnLoadMethodAttribute() { }
+        public RuntimeInitializeOnLoadMethodAttribute(RuntimeInitializeLoadType loadType) { }
+    }
+}
+
+// Sub-namespace anchors (referenced via `using`; types unmask in later waves if used).
+namespace UnityEngine.Experimental { internal class _ShimAnchor { } }
+namespace UnityEngine.Experimental.Rendering { internal class _ShimAnchor { } }
+namespace UnityEngine.SceneManagement { internal class _ShimAnchor { } }
+namespace UnityEngine.SocialPlatforms
+{
+    // NOTE: no IAchievementCallback here -- the engine's AchievementImpl uses
+    // Cute.IAchievementCallback; adding one here makes the unqualified name ambiguous.
+    public interface IAchievement { }
+    public interface IAchievementDescription { }
+}