The /climate/<city>[/month|/records] pages render from the content
derived-store keyed by content_token (PAYLOAD_VER:CONTENT_VER:archive
last-date), which turns over ~daily when a cell's archive gains a day.
On the first request after each advance the page recomputed a 45-year
payload cold.
Add warm_cities.warm_content: for each curated city, compute the cheap
content token and check whether every content kind (city, 12 months,
records) already has a fresh row; cities wholly fresh are skipped without
loading the archive, so a re-run is near-instant and only cells whose
archive advanced do work. Cache-only like main() — a cell with no cached
archive is skipped, never fetched, so warming spends no upstream quota.
A per-call limit caps cities (re)built so one pass's wall-clock is
bounded; the idempotent skip resumes on the next call.
Ride it on the leader-gated notifier loop next to the homepage sweep:
_maybe_warm_content runs at most every 30 min, capped at 50 cities per
tick, so a tick can't stall the notifier and the ~1000-city set refreshes
across a handful of ticks — well inside the <=1-day staleness the token
already tolerates.
