Reuse resolvedPathname from prepare (#81194)
This applies the fixed `resolvedPathname` from
https://github.com/vercel/next.js/pull/81144 to the other route handlers
that were trying to build this value as well so we use single source of
truth.
Validated against our deploy tests
https://github.com/vercel/vercel/actions/runs/16038359282/job/45254959257?pr=13520
and
https://github.com/vercel/next.js/actions/runs/16038663582/job/45255920639
