feat: Added IAssignable.Unassign()

Engine.Core/GameManager.cs

@@ -14,6 +14,7 @@ public class GameManager : IInitialize
 {
     public Action<IInitialize>? OnInitialized { get; set; } = null;
     public Action<IInitialize>? OnFinalized { get; set; } = null;
+    public Action<IAssignable>? OnUnassigned { get; set; } = null;
     public Action<IAssignableStateEnable>? OnStateEnableAssigned { get; set; } = null;
 
 
@@ -98,6 +99,16 @@ public class GameManager : IInitialize
         return true;
     }
 
+    public bool Unassign()
+    {
+        if (Initialized)
+            return false;
+
+        _stateEnable = null!;
+        OnUnassigned?.Invoke(this);
+        return true;
+    }
+
     public void Update(GameTime time)
     {
         foreach (var gameObject in GameObjects)