Review follow-ups on the column-overflow scenario:
- Memoize the sweep so the golden and the assertions consume the same
readings, which is what its contract already claimed; two runs could
disagree if a resize settled differently between them.
- Settle the column width before the mutation control measures. The test
arrives from 1680 alone and from the sweep's 600 in a full run, and the
frame eases its column tracks, so an immediate read can report the
previous viewport's bleed.
- Name the wheel delta, assert the bleed stays inside it, and compare the
travelled distance rounded: a clamp or a sub-pixel would otherwise read
as a broken fix.
creatixchu
94e2c8129d