Improve Partial Prefetching adoption checks (#97637)
## Summary
Dogfooding the Partial Prefetching adoption skill on v0 exposed two
preservation checks that should be part of the main workflow:
- trace custom Link wrapper consumers and distinguish declarative
prefetch props from imperative hover or touch prefetching
- treat existing instant() assertions as preservation contracts, and
expand caching only to the smallest coherent rendered subtree when a
data-only cache does not restore the prefetched UI
## Verification
- pnpm prettier --with-node-modules --ignore-path .prettierignore
--check skills/next-partial-prefetching-adoption/SKILL.md
- Commit hook lint-staged formatting passed
- Not run: quick_validate.py because PyYAML is unavailable in the local
skill validator runtime
<!-- NEXT_JS_LLM -->
