### Overview Links in the body text of the user documentation return 404 on the deployed site. For example, the "Translations" link in the body of the Guides page (https://project.pages.drupalcode.org/canvas/guides/) points to `/guides/translations` instead of `/canvas/guides/translations`, so it 404s. The same "Translations" link in the left sidebar works. The documentation is deployed under a base path that is only known at build time: `/canvas/` in production and a nested `/canvas/mr-<iid>/` for merge request previews. Hardcoded root-relative Markdown links in the content are emitted without that base, so they resolve to the domain root and 404. Sidebar links are unaffected because Starlight resolves them against the base path. This affects in-content links across all documentation sections, not only the Guides page. Because the base is dynamic (and nested for previews), hardcoding it into each link is not viable — the correct base can only be applied at build time. ### Steps to reproduce 1. Open https://project.pages.drupalcode.org/canvas/guides/ 2. Click the "Translations" link in the page body. 3. Result: 404 Not Found. The sidebar "Translations" link works. ### Proposed resolution Apply the configured base path to in-content links at build time. A rehype plugin prefixes the build-time base to root-relative in-site links, so they resolve correctly on every deploy target (production and per-MR previews) while the source markup stays base-agnostic. External, protocol-relative, anchor, and already-prefixed links are left untouched. ### Remaining tasks - Add link checking to the docs build so broken links fail before deploy (follow-up). ### User interface changes None (documentation only).