The unit battery derives rollup fixtures in JS; this pins the same
parity through the pipe itself. Seed raw measurements, read the tiered
fetch before the fold (coverage miss, raw path baseline), fold with the
real recomputeUserRollups DAY pass, read again, and assert the two
daily series are equivalent — including a dual-source weight day whose
per-source rows must compose to the all-source mean. A drifted writer
projection, coverage-probe SQL, or bucket compose surfaces here.
