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/Engine/INetworkLogger.cs

@@ -0,0 +1,13 @@
+using System.Collections;
+using System.Collections.Generic;
+
+public interface INetworkLogger<out T> : IEnumerable<T>, IEnumerable
+{
+	void LogInfo(string text);
+
+	void LogWarning(string text);
+
+	void LogError(string text);
+
+	void ClearLog();
+}

SVSim.BattleEngine/Engine/SingletonMonoBehaviour.cs

@@ -0,0 +1,43 @@
+using UnityEngine;
+
+public class SingletonMonoBehaviour<T> : MonoBehaviour where T : MonoBehaviour
+{
+	private static T _instance;
+
+	protected bool _isRedy;
+
+	public static T instance
+	{
+		get
+		{
+			if (_instance == null)
+			{
+				_instance = (T)Object.FindObjectOfType(typeof(T));
+				if (_instance == null)
+				{
+					Debug.LogError(typeof(T)?.ToString() + "is nothing");
+				}
+			}
+			return _instance;
+		}
+	}
+
+	public bool isRedy => _isRedy;
+
+	public static bool IsInstanceEmpty()
+	{
+		return _instance == null;
+	}
+
+	private void Awake()
+	{
+		if (_instance == null)
+		{
+			_instance = (T)Object.FindObjectOfType(typeof(T));
+			if (_instance == null)
+			{
+				Debug.LogError(typeof(T)?.ToString() + "is nothing");
+			}
+		}
+	}
+}