docs: document React.cache pattern for sharing params without prop drilling
Add documentation showing how to use React.cache to create a params()
helper that lets any Server Component in the subtree access route params
without receiving them as props — similar to cookies() and headers().
Includes an e2e test fixture validating the pattern works in both dev
and production modes. Also documents why Next.js doesn't provide this
as a built-in: params are per-segment (not per-request like cookies),
creating ambiguity with parallel routes.
https://claude.ai/code/session_016vaJJpmrxH9CuqfCwRLshy