feat: add Laravel 13 support - illuminate/contracts: ^12.0||^13.0 (drop bare ^12.0) - orchestra/testbench: ^10.6||^11.0 - laravel/tinker: auto-bumped to ^3.0 (L13 transitive) - CI matrix: Laravel 12.* + 13.* × PHP 8.3 + 8.4 - HasUserRelation trait: property_exists instead of ?? - phpstan level 6 clean Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>