Codify the lessons from the subprocessors filter fix as reusable guidance:
a pure URL-state filter hook (never a per-instance mirror + write-back
effect), a single-owner debounced search hook, and refetching inside a
transition to scope the loading state to the results instead of the
whole-page Suspense fallback.
Add a list-filtering Cursor rule and expand the state-management and relay
guides with the corresponding sections.
Signed-off-by: Émile Ré <emile@probo.com>
8ed92e13b3