Fix docs trailing-slash URLs and improve mobile API navigation

[aivascu]

Summary

• Fix docs pages showing no content when GitHub Pages serves a trailing-slash URL by normalizing paths in a global route middleware and stripping trailing slashes before content queries
• Show API package picker, version select, and API table of contents in the mobile header menu on API routes
• Regenerate site/package-lock.json with npm 11

Test plan

• Open a docs page with and without a trailing slash (for example /docs/getting-started/ vs /docs/getting-started) and confirm content renders in both cases
• On mobile viewport, open the header menu on an API page and confirm package picker, version select, and API navigation appear
• Run npm ci and npm run generate in site/ to verify the regenerated lockfile installs cleanly