The stylelint CI only checks /css directory and uses drupal core .prettierrc.json configuration instead of canvas.

Overview

While fixing issue #3566392: Keep Canvas' own `.prettierrc.json` only for linting JS, ignore it for linting CSS, we discovered that the stylelint CI job has two critical issues:

1. Limited scope: It only runs linting for CSS files in the root-level /css folder, completely missing CSS files in other directories like /ui.
2. Configuration Update: The CI pipeline uses .prettierrc.json from Drupal core. Ensure it uses project's own configuration.

Steps to reproduce

• Create an MR and make any css files and you'll see styelint CI job is triggerd.
• Observe that it logs following:
  

  4 sources checked
    /builds/issue/canvas/web/modules/custom/canvas/css/autocomplete.extend.css
    /builds/issue/canvas/web/modules/custom/canvas/css/canvas-cta.css
    /builds/issue/canvas/web/modules/custom/canvas/css/menu-icons.css
    /builds/issue/canvas/web/modules/custom/canvas/css/navigation-override.css
  

• Note in above logs the CSS files in /css directory are only included and potentially other directories are not included. Ex: /ui directory.

Proposed resolution

• Investigate why the stylelint CI job is limited to the root /css folder.
• Update the stylelint CI configuration to:
  • Include CSS files from all directories (including css files from /ui directory).
  • Use Canvas project's .prettierrc.json configuration instead of Drupal core.
• Fix any linting errors discovered in the newly-scanned directories
• Verify that the updated CI job successfully checks all CSS files across the project using the correct configuration.
• Update documentation if needed.