feat: Navigate the back office with HTMX

Problem/Motivation

Every click in the back office reloads the whole page, rail and top bar included.

Steps to reproduce

• Sign in and open any back office screen.
• Click a link in the rail or apply an exposed filter, pager or sort on a listing.
• The whole page reloads instead of just the content.

Proposed resolution

Boost the links and the GET forms (exposed filters, pagers, sorting) with Drupal core HTMX, swapping only the page and keeping the rail. Keep full page loads for the edit, add and delete forms and the screens with drag and drop or builders. Move the focus to the content and announce the new page after each swap. A theme setting turns it off. Cover with webship-js tests.

Remaining tasks

• ☑ 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
• ☐ Documentation
• ☐ Code review by maintainers
• ☐ Full testing and approval
• ☐ Credit contributors
• ☐ Review with the product owner
• ☐ Release notes
• ☐ Release

API changes

N/A

Data model changes

N/A

Release notes snippet

N/A

AI-Generated: Yes