fix: keep borderless form widgets borderless under an app's theme - #160

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: actions/checkout@v2, VeryGoodOpenSource/very_good_coverage@v1. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/