fix(Link): memoize merged ref to prevent unnecessary ref callback invocations

[wataryooou]

Link calls mergeRefs(forwardedRef, prefetchRef) inline in JSX, so a new RefCallback is created on every render. React sees the ref identity change and calls the old ref with null then the new ref with the DOM node — even if the consumer passes a stable ref callback. This causes the ref to be invoked twice on every re-render (#12705).

Fixed by wrapping in useMemo:

let mergedRef = React.useMemo(
  () => mergeRefs(forwardedRef, prefetchRef),
  [forwardedRef, prefetchRef],
);

useMemo fits here since we're memoizing the return value of mergeRefs, not a user callback. prefetchRef comes from useRef so it's stable, and forwardedRef only changes when the parent passes a different ref — so mergedRef stays the same across normal re-renders.

Added two tests: one for a plain state-driven re-render, and one for prefetch="intent" with mouseenter/mouseleave triggering re-renders via FrameworkContext.

Fixes #12705

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[changeset-bot]

🦋 Changeset detected

Latest commit: f988a43

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 11 packages

Name	Type
react-router	Patch
@react-router/architect	Patch
@react-router/cloudflare	Patch
@react-router/dev	Patch
react-router-dom	Patch
@react-router/express	Patch
@react-router/node	Patch
@react-router/serve	Patch
@react-router/fs-routes	Patch
@react-router/remix-routes-option-adapter	Patch
create-react-router	Patch

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[remix-cla-bot]

Thank you for signing the Contributor License Agreement. Let's get this merged! 🥳

[timdorr]

As long as the tests pass, looks good to me.