The daily-series reader only fell back to live SQL on a coverage MISS
(zero rollup rows); a transient rollup-table error (statement_timeout,
deadlock, connection reset) was unwrapped and 500'd the tile on the
single-type route even though live SQL could serve it — and diverged from
the batched series route, which already caught. Wrap the primary daily
read and the long-range tiered read: treat a throw as a coverage miss and
fall through to the live date_trunc aggregate.