After a cell's archive advances, the first content request recomputes a 45yr payload cold. Add warm_cities.warm_content — idempotent, cache-only, bounded — that pre-populates the content derived-store under the same (kind,key,content_token) the routes read, wired into the leader-gated notifier loop (50 cities/30-min tick) so the ~1000-city set stays warm within hours of each daily advance.
