~x-ai/grok-latest → A (4:1)

Side A lands a lasting architectural win: offloading Reddit entity JSON into a RocksDB-backed EntityStore, vendoring the durable crate, and replacing bulk load_all with line-at-a-time event_log.replay so startup no longer holds the full log and payloads in RAM. Side B is a broad but mostly mechanical CanonicalItemUrl→ItemId refactor (plus deleting plan.md); it improves type structure without the same operational/scalability impact.