LOOM-2442 Pt 2 React 19 migration

[Simon Ward (Sybsw)]

LOOM-2442

Finishes making the React 19 jest matrix green so it can be flipped to required.

• react-transition-group nodeRef migration — R19 removed findDOMNode, which / fall back to without nodeRef. Added refs in 4 components:
  • BpkFloatingNotification — useRef on the wrapping
  • BpkDrawerContent — local nodeRef plus a setRefs callback that also forwards to the existing dialogRef prop
  • AnimateAndFade (banner-alert + info-banner) — class-field nodeRef injected onto the single-element child via cloneElement
• withInfiniteScroll test stabilisation — wrapped updateData(...) and intersect() calls in act(async () => …) so state flushes deterministically across both React versions. Regenerated 3 snapshots that were
  latently stale on R18 (they were captured before the data refresh actually applied — the test name said "should refresh data" but the snapshot showed pre-refresh DOM).

All tests passing, snapshots working

npm run lint and npm run typecheck clean on both versions.

Follow-ups (not in this PR)

• Flip the React19 CI job from continue-on-error: true to required after this lands and stays green on main for a run or two.
• Remaining deferred items from LOOM-2442 Pt 1 React 19 Migration #4455 (class-component defaultProps, Flow prop-types removal, @types/react@19 bump) are independent threads.

Remember to include the following changes:

• Ensure the PR title includes the name of the component you are changing so it's clear in the release notes for consumers of the changes in the version e.g [Clover-123][BpkButton] Updating the colour
• README.md (If you have created a new component)
• Component README.md
• Tests
• Accessibility tests
  • The following checks were performed:
    • Ability to navigate using a keyboard only
    • Zoom functionality (Deque University explanation):
      • The page SHOULD be functional AND readable when only the text is magnified to 200% of its initial size
      • Pages must reflow as zoom increases up to 400% so that content continues to be presented in only one column i.e. Content MUST NOT require scrolling in two directions (both vertically and horizontally)
    • Ability to navigate using a screen reader only
• Storybook examples created/updated
• For breaking changes or deprecating components/properties, migration guides added to the description of the PR. If the guide has large changes, consider creating a new Markdown page inside the component's docs folder and link it here