Published mobile stacking is the global RESPONSIVE_CSS rule matching the
DESKTOP inline style, so un-stacking Columns on mobile under a stacked tablet
(styleMobile.flexDirection 'row') publishes un-stacked. The editor's
device-emulation copy matched the resolved inline style and showed it stacked.
RenderNode now marks nodes with a flexDirection/display override with
data-wsb-base-stack (baseStacksOnMobile) and editor.css keys off it.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>