Make GitBook the sole scroll authority so cross-page anchors land on target (RND-11844)

Browser diagnostics on the reported n8n case showed two cooperating causes, which is
why the earlier single-sided attempts failed:

1. The scroll hooks fire when the hash is set (on link click, still on the previous
   page), so the target heading isn't in the DOM yet and scrollToHash missed and never
   retried. Fixed in the previous commit by retrying scrollToHash across frames.
2. With the retry in place, our scrollIntoView *does* fire once the heading commits —
   but Next's own post-navigation scroll (its hash scrollIntoView plus a scroll-to-top,
   see useHash / vercel/next.js#49465) runs after us and wins, snapping back to the top.

Set `scroll={false}` on the internal NextLink so Next stops managing scroll on
client-side navigation and GitBook's ScrollPage/useScrollToHash own it exclusively:
retry to the hash when present, scroll to top otherwise. Neither change works alone —
the retry needs Next to stop overriding it, and scroll={false} needs the retry to find
the late-committing element.

Still needs a browser check: rerunning the console diagnostic should now show our
scrollIntoView fire without a following scroll-to-top, landing on the heading. Because
scroll={false} routes all navigation scroll through ScrollPage, also regression-check
plain page-to-page nav (top), same-page anchors, and back/forward.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01TpGe6QkAF4Y1HDGUD4vbke

packages/gitbook/src/components/primitives/Link.tsx

@@ -171,6 +171,12 @@ export function Link(props: LinkProps) {
             ref={ref}
             href={href}
             prefetch={_prefetch}
+            // GitBook is the sole scroll authority on client-side navigation (`ScrollPage` /
+            // `useScrollToHash` → `scrollToHash`, which retries until the target commits). Next's
+            // own post-navigation scroll (see `useHash`, vercel/next.js#49465) otherwise fires its
+            // own `scrollToHash` and a scroll-to-top that override ours, leaving cross-page anchor
+            // links stuck at the top. Opt out so only our handlers scroll.
+            scroll={false}
             className={tcls(...forwardedClassNames, className)}
             {...domProps}
             onClick={onClick}