TDD Godot with VS2026 through 2dog

Perhaps we could not rethink how VS2026 could support TDD with Godot4 in .NET

https://github.com/outfox/2dog/issues/4

```c#
using twodog.xunit;

[Collection("GodotHeadless")]
public class GodotSceneTests(GodotHeadlessFixture godot)
{
[Fact]
public void LoadScene_ValidPath_Succeeds()
{
var scene = GD.Load("res://game.tscn");
var instance = scene.Instantiate();

godot.Tree.Root.AddChild(instance);

Assert.NotNull(instance.Parent);
}
}
```