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/asserts/GdUnitGodotErrorWithAssertTest.gd

@@ -0,0 +1,38 @@
+extends GdUnitTestSuite
+
+
+var _catched_events: Array[GdUnitEvent] = []
+
+
+func test_assert_method_with_enabled_global_error_report() -> void:
+	ProjectSettings.set_setting(GdUnitSettings.REPORT_SCRIPT_ERRORS, true)
+	assert_error(do_a_fail).is_runtime_error('Assertion failed: test')
+
+
+func test_assert_method_with_disabled_global_error_report() -> void:
+	ProjectSettings.set_setting(GdUnitSettings.REPORT_SCRIPT_ERRORS, false)
+	assert_error(do_a_fail).is_runtime_error('Assertion failed: test')
+
+
+func do_a_fail() -> void:
+	@warning_ignore("assert_always_false")
+	assert(3 == 1, 'test')
+
+
+func catch_test_events(event :GdUnitEvent) -> void:
+	_catched_events.append(event)
+
+
+func before(
+	_do_skip := Engine.is_embedded_in_editor() or OS.is_debug_build(),
+	_skip_reason  := "Is skipped because the test will holt on script error in debug mode"
+	) -> void:
+
+	GdUnitSignals.instance().gdunit_event.connect(catch_test_events)
+
+
+func after() -> void:
+	# We expect no errors or failures, as we caught already the assert error by using the assert `assert_error` on the test case
+	assert_array(_catched_events).extractv(extr("error_count"), extr("failed_count"))\
+		.contains_exactly([tuple(0, 0), tuple(0,0), tuple(0,0), tuple(0,0)])
+	GdUnitSignals.instance().gdunit_event.disconnect(catch_test_events)