Fixes https://github.com/vercel/next.js/issues/54240
The Link component in App Router is not respecting `scroll-behavior: smooth` when only the hash changes.
It appears to be caused by `focusAndScrollRef.onlyHashChange = false` being set before `handleSmoothScroll` is called, causing `htmlElement.style.scrollBehavior` to be overridden to `auto` before `scrollIntoView` is called.
Moving `focusAndScrollRef.onlyHashChange = false` to after `handleSmoothScroll` invocation resolves the issue.
42abfd694d