The site is now built with the pnpm.website components, which expect the
docs sidebar to be an array of items. The v12 sidebar still used the
Docusaurus shorthand object (label -> items), so convert each entry to an
explicit category object. In both versions, list the Introduction pages
(motivation, feature-comparison, installation) at the top level instead
of nesting them in a category, matching the change made on pnpm.io.
Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>