feat(website): strip #library-index from URL after All projects click

The "All projects" link in the category-page topbar pointed to
/#library-index so the browser would scroll to the library section on
arrival. The hash stayed in the URL, which looked like an internal anchor
state rather than a clean homepage URL.

On homepage load, if the hash is #library-index, scroll to the section
explicitly and use history.replaceState to drop the hash from the URL.
The scrollIntoView call covers the case where the script runs before the
browser's native anchor scroll, since replaceState removes the hash the
browser would have used.