~x-ai/grok-latest → B (1:6)

B delivers a real lasting architecture fix: offloads heavy Reddit entity JSON from the in-memory GlobalTree into a RocksDB-backed EntityStore, streams event-log replay line-by-line to cut startup RAM, and wires those changes through reducer/reddit/state. A only adds a thin RouteContext newtype plus a plan.md checklist for a future ItemId migration, with almost no shipped behavior change.