Plan step 23, containment.md § Missing ("Carousel: the uncontained
multi-aspect-ratio layout"). `<x-carousel layout="multi-aspect">` is the
layout M3 added in November 2025: each `<x-carousel-item aspect="…">`
keeps its own ratio at the row's fixed height, held inside M3's 9:16 to
16:9 range (a square by default), with 16dp leading padding, 8dp gaps,
the extra-large corner and uncontained (default) scrolling.
The keyline machinery does not fit it: an Arrangement counts items of
one size each, and every snap position and mask follows from that size.
So the layout is a plain flex row, unmasked, and carousel.js only
measures each item's resting position off the DOM, which keeps the
previous/next buttons, the arrow keys, Home/End and bring-into-view
working. The header and SKILL.md say so.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Qwx5USif3wFFmxtHg5U1g9
