Introduce data-icon-swap attribute with paired outline/fill <i> elements.
CSS toggles to filled icon on hover and active state. Module slots
auto-derive fill variant from icon name, with explicit icon_fill override
for icons without a fill counterpart (e.g. bi-headset). Add enforcement
script bin/icon-swap-check.sh.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>