Use GetMut in Entity.Set to avoid unnecessary copy

src/gaemstone.ECS/EntityRef.cs

@@ -116,8 +116,8 @@ public unsafe class EntityRef
 
 	public override ref T GetMut<T>(Id id)
 	{
+		// Value is added if it doesn't exist on the entity.
 		var ptr = ecs_get_mut_id(World, this, id);
-		// NOTE: Value is added if it doesn't exist on the entity.
 		return ref Unsafe.AsRef<T>(ptr);
 	}
 
@@ -125,22 +125,13 @@ public unsafe class EntityRef
 		=> ecs_modified_id(World, this, id);
 
 	public override EntityRef Set<T>(Id id, in T value)
-	{
-		var size = (ulong)Unsafe.SizeOf<T>();
-		fixed (T* ptr = &value)
-			if (ecs_set_id(World, this, id, size, ptr).Data == 0)
-				throw new InvalidOperationException();
-		return this;
-	}
-
+		{ GetMut<T>(id) = value; return this; }
 	public override EntityRef Set<T>(Id id, T obj) where T : class
 	{
 		if (obj == null) throw new ArgumentNullException(nameof(obj));
-		var size = (ulong)sizeof(ReferenceHandle);
-		// Dispose this handle afterwards, since Flecs clones it.
-		using var handle = ReferenceHandle.Alloc(obj);
-		if (ecs_set_id(World, this, id, size, &handle).Data == 0)
-			throw new InvalidOperationException();
+		ref var handle = ref GetMut<ReferenceHandle>(id);
+		handle.Dispose(); // Free previously handle, if any.
+		handle = ReferenceHandle.Alloc(obj);
 		return this;
 	}