chore(client): add gdUnit4 test framework addon

Vendor gdUnit4 for Godot 4 client testing (D-030).

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

client/addons/gdUnit4/test/core/GdUnitToolsTest.gd

@@ -0,0 +1,49 @@
+# GdUnit generated TestSuite
+class_name GdUnitToolsTest
+extends GdUnitTestSuite
+
+const GdUnitTools := preload("res://addons/gdUnit4/src/core/GdUnitTools.gd")
+
+# TestSuite generated from
+const __source = 'res://addons/gdUnit4/src/core/GdUnitTools.gd'
+
+
+class InnerTestNodeClass extends Node:
+	pass
+
+class InnerTestRefCountedClass extends RefCounted:
+	pass
+
+
+func test_free_instance() -> void:
+	# on valid instances
+	assert_bool(await GdUnitTools.free_instance(RefCounted.new())).is_true()
+	assert_bool(await GdUnitTools.free_instance(Node.new())).is_true()
+	assert_bool(await GdUnitTools.free_instance(JavaClass.new())).is_true()
+	assert_bool(await GdUnitTools.free_instance(InnerTestNodeClass.new())).is_true()
+	assert_bool(await GdUnitTools.free_instance(InnerTestRefCountedClass.new())).is_true()
+
+	# on invalid instances
+	assert_bool(await GdUnitTools.free_instance(null)).is_false()
+	assert_bool(await GdUnitTools.free_instance(RefCounted)).is_false()
+
+	# on already freed instances
+	var node := Node.new()
+	node.free()
+	assert_bool(await GdUnitTools.free_instance(node)).is_false()
+
+
+func test_richtext_normalize() -> void:
+	assert_that(GdUnitTools.richtext_normalize("")).is_equal("")
+	assert_that(GdUnitTools.richtext_normalize("This is a Color Message")).is_equal("This is a Color Message")
+
+	var message := """
+		[color=green]line [/color][color=aqua]11:[/color] [color=#CD5C5C]Expecting:[/color]
+			must be empty but was
+		'[color=#1E90FF]after[/color]'
+		"""
+	assert_that(GdUnitTools.richtext_normalize(message)).is_equal("""
+		line 11: Expecting:
+			must be empty but was
+		'after'
+		""")