chore(client): vendor GUT 9.7.1 + headless test harness

client/run_tests.sh

@@ -0,0 +1,8 @@
+#!/usr/bin/env bash
+# Headless GUT runner. Imports the project first so global class_name refs
+# resolve on a fresh checkout / after new class_name scripts are added.
+# Fallback if --import misbehaves on some builds: godot --headless --editor --quit
+set -uo pipefail
+cd "$(dirname "$0")"
+godot --headless --import >/dev/null 2>&1 || true
+godot --headless -s res://addons/gut/gut_cmdln.gd -gconfig=res://.gutconfig.json "$@"