Fix - Add to Cart button is taller than the quantity input on single product page - #69

Process completed with exit code 1.

This PR changes product source but adds no regression spec — refusing before spending runner minutes. See the PR comment.

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: actions/checkout@v4. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/