Sprint E: homepage section editor now filters the layout-strategy picker
to each widget's widget-manifest.json supportedLayouts instead of always
showing all 5 strategies. columns field gated to widgets that read it
(hero, product-collection carousel).
Sprint F: closes client bug report (no items-per-page control, hero
carousel not manually/automatically scrollable, no 1-2 slide big-carousel
option). Product carousel item width now driven by layout.columns
(reused, was already editable but dead). Hero widget gains prev/next
arrows, touch swipe, and 1-2 panel mode via the same field.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>