Simon a9893068cd Don't re-anchor the grid on height-only viewport changes ...

The settle window I added for rotation also ran for every `resize`, and
on a phone the URL bar collapsing during a fast flick is exactly that.
It re-asserted an anchor captured before the flick, so a scrollTo landed
mid-momentum and stopped the scroll dead.

Only a width change (or an orientationchange) can move a card: positions
are absolute pixels in the grid's own space, so a height-only resize
leaves both the layout and the scroll position correct and needs no
restore at all. The one exception kept is a scrollbar appearing on
desktop, which changes the grid's inner width while window.innerWidth
stays put -- that re-packs, but only when the columns actually moved.

Modelled the failure in headless Chrome (height change mid-flick, scroll
continuing): the flick was yanked back 173px before, and now runs on to
where it was headed. Rotation still re-anchors, and a fast scroll with 80
videos loaded holds 60fps (median 16.7ms/frame, max 17.2ms, no frame
over 32ms).

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01QBDkEXP4htyXTCZUwMLphd

2026-09-05 15:15:44 +00:00

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