chore(tooling): install GUT v9.6.0 test framework

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

addons/gut/godot_singletons.gd

@@ -0,0 +1,48 @@
+
+# This file is auto-generated as part of the release process.  GUT maintainers
+# should not change this file manually.
+static var class_ref = [
+	AudioServer,
+	CameraServer,
+	ClassDB,
+	DisplayServer,
+	# excluded: EditorInterface,
+	Engine,
+	EngineDebugger,
+	GDExtensionManager,
+	Geometry2D,
+	Geometry3D,
+	IP,
+	Input,
+	InputMap,
+	JavaClassWrapper,
+	JavaScriptBridge,
+	Marshalls,
+	NativeMenu,
+	NavigationMeshGenerator,
+	NavigationServer2D,
+	NavigationServer2DManager,
+	NavigationServer3D,
+	NavigationServer3DManager,
+	OS,
+	Performance,
+	PhysicsServer2D,
+	PhysicsServer2DManager,
+	PhysicsServer3D,
+	PhysicsServer3DManager,
+	ProjectSettings,
+	RenderingServer,
+	ResourceLoader,
+	ResourceSaver,
+	ResourceUID,
+	TextServerManager,
+	ThemeDB,
+	Time,
+	TranslationServer,
+	WorkerThreadPool,
+	XRServer
+]
+static var names = []
+static func _static_init():
+	for entry in class_ref:
+		names.append(entry.get_class())