Add a fourth reusable workflow for themes' visual.yml (THEMES.md section 18.1)

standards/THEMES.md §18.1 requires a theme repository to ship four workflows — install.yml, tests.yml, compatibility.yml and visual.yml — against a module's three.

There is no reusable package-visual.yml in this repository, and no theme in the fleet has a visual.yml at all.

Ask

A fourth reusable workflow covering what §18.1 asks of it: visual regression and accessibility checks. Pseudo-localization and RTL direction checks belong here too — TRANSLATIONS.md and THEMES.md §18.1 both require them, and they are theme-shaped rather than module-shaped, so splitting them from the module test workflow keeps each check in the repository that can fail it.

Context

ecommerce-laravel creates a theme-ecommerce in the first wave of its migration, and per-merchant child themes after that. Each will need this workflow, and the standard already names it, so the alternative is every theme author writing their own.

Worth noting the downstream decision this interacts with: ecommerce-laravel is shipping en only, which leaves the RTL requirement in both standards deliberately unexercised. A working visual.yml is what would make exercising it cheap later.

Found while planning theme packaging for ecommerce-laravel.

Start by reading standards/THEMES.md §18.1 and the relevant requirements in TRANSLATIONS.md, then inspect the existing reusable workflows to understand their structure. Add the missing package-visual.yml workflow with visual regression, accessibility, pseudo-localization, and RTL checks. Done means theme repositories can reuse it to cover every check named by the standards.