Window to report run-minutes over, half-open as [startTime, endTime). Both bounds
are unix seconds and must be midnight UTC - a whole multiple of 86400 - because the
rollup is per-UTC-day. A bound that is not midnight is rejected rather than rounded,
so being a few hours off cannot silently drop a day. The span may be at most 62 days.
- startTimeInclusive lower bound. Days older than the rollup's retention horizon (~183 days) hold no data and report zero.
- endTimeExclusive upper bound, clamped to the start of today: the rollup only covers days that have closed, so today is never reported. A window entirely in the future is not an error - it reports an empty window and no data.