Migrate to new Button module with shape variants
Source Button and ButtonWithTooltip from the new module (with
ButtonWithPopover) instead of the legacy module. Update all consumers
to use the new variant/size/shape API (ghost→tertiary, iconMd→md+circle,
rounded→shape="circle"). Add forbidden bare-HTML-elements rule.
BetterImagine: Use native button variants, fix pluralize double-number bug
Drop custom chip/chip-danger CSS from toolbar buttons in favor of native
tertiary/danger variants. Bump toolbar buttons to size md to match Grok
nav buttons. Fix pluralize() being called with a redundant count prefix
causing "11 item" instead of "1 item". Disable Select, Delete all, and
Download all when no visible items exist.