PPR pages lose cache after `next start` restart and RSC payload serves stale build-time data due to missing `.rsc` file in file-system-cache
File-system-cache `set()` omits the `.rsc` file for PPR routes, causing `get()` to treat the entry as missing after restart or eviction. This results in fallback shell re-rendering and stale RSC payloads for client navigation, leading to data inconsistency.
