task: #3620353 Install the front-end libraries with Composer, not drupal-libraries-sync

Issue: https://www.drupal.org/project/horizonaid/issues/3620353

What and why

Varbase 11 used to get six front-end libraries by running scripts/drupal-libraries-sync.js, a Node script that copied files out of node_modules/ into web/libraries/, driven by a drupal-libraries block plus six npm dependencies and a postinstall hook in package.json. That is replaced by Composer packages on Packagist, each required by the module or the varbase_* recipe that actually loads it: vardot/aos 2.3.4, vardot/jquery.fancytree 2.38.5, vardot/ckeditor5-media-embed-drupal 47.6.2, vardot/ace 1.44.0 and vardot/dropzone 5.9.3 (all type: drupal-library, all on Packagist), plus swagger-api/swagger-ui, which drupal/openapi_ui_swagger already required and which only needed an installer path.

Horizon Aid is the only one of the site templates whose wiring for this script was still live, so this is the one that actually changes CI behaviour.

• Removes scripts/drupal-libraries-sync.js and scripts/assets/drupal-libraries.package.json (which existed only to feed that sync).
• Rewires the Drupal CMS pre-test job in .gitlab-ci.yml: it no longer writes a package.json, no longer copies the script in, and no longer runs yarn at all.
• Requires mnsami/composer-custom-directory-installer and wires the two installer paths a generic web/libraries/{$name} rule cannot place: web/libraries/swagger-ui for swagger-api/swagger-ui (which is type: library, not drupal-library), and the nested web/libraries/ckeditor5/plugins/media-embed that drupal/ckeditor_media_embed loads from.
• Asserts the library files the .libraries.yml entries load are on disk, instead of counting entries in a package.json block. A count could pass while an installer path was wrong or an upstream layout had changed.

Verified on a freshly installed Varbase 11.4.5 site in DDEV with the packages resolved from Packagist and no VCS repositories: 14/14 declared library files present, 10/10 assets HTTP 200, 7/7 Drupal libraries discovered with every asset resolving, status report green, and yarn install succeeds with none of the six npm library packages present.

AI-Generated: Yes

Checkpoints:

• File an issue
• Addition/Change/Update/Fix
• Testing to ensure no regression
• Automated unit testing coverage
• Automated functional testing coverage
• UX/UI designer responsibilities
• Readability
• Accessibility
• Performance
• Security
• Developer Documentation
• User Guide Documentation
• Reviewed by human
• Code review by maintainers
• Full testing and approval
• Credit contributors
• Review with the product owner
• Release notes snippet
• Release