Let a rune's collapsed (mobile) form be a carousel instead of a stack — a CSS-only arrangement flip at the SPEC-099 collapse breakpoint, with no JS nav on the responsive path. Per SPEC-100 Phase A.4.
Tracking started Jun 25 — check back for trends.
collapse-to dial (stack | carousel, default stack) that selects the collapsed form. It is orthogonal to collapse (the breakpoint) — not a second breakpoint, so consistent with SPEC-099's "no second layout-collapse attribute" rule.collapse-to="carousel": below the collapse breakpoint the item band flips from its base arrangement (grid/list) to a scroll-snap row — CSS-only, keyed off the same collapse hook (WORK-469). layout="carousel" is already a carousel at all widths, so collapse-to is moot there.layout="carousel"); the responsive collapse path relies on native touch/trackpad scroll and does not mount the JS affordances.matchMedia mount/unmount lifecycle in the behavior layer (non-goal).collapse-to dial (stack | carousel, default stack) selects the collapsed form, orthogonal to the collapse breakpoint; layout="grid" collapse-to="carousel" is grid above the breakpoint and a swipe row below.collapse breakpoint.matchMedia mount/unmount in the behavior layer and no JS nav chrome mounted on the responsive collapse path.collapse hook (no new breakpoint attribute).collapse hook the flip keys off.collapse semantics).