docs: add note on React canary version to View transitions guide (#92315)
## Summary
Addresses a DX friction log finding and two minor clarifications in the
view transitions guide.
### Changes
- Add note explaining that `import { ViewTransition } from 'react'`
works because Next.js rewrites it to its internal React canary build via
bundler aliases (friction log finding)
- Clarify that shared element morph works without any CSS; `share` is
only needed to customize the animation
- Minor formatting fix in Next steps links
## Test plan
- [ ] Verify guide renders correctly in docs preview
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Co-authored-by: Joseph <joseph.chamochumbi@vercel.com>
Co-authored-by: vercel[bot] <35613825+vercel[bot]@users.noreply.github.com>