The keyed refold's day filter and delete compared the naive UTC
measured_at and bucket_start with a timestamptz[] parameter, which goes
through the session time zone; in any zone but UTC neither matched and
the refold left its buckets stale. Both now bind timestamp[] literals.
Keys are refolded in (type, day) order in chunks of 500, and the
rollup-recompute queue describes the runs of buckets a job now covers.
