Nav typology icons + expand fix

Wired @antora-supplemental/nav-typology and nav-typology-diataxis (same stack as docs.devcentr.org) so Diátaxis / changelog sidebar rows get uniform SVG icons.

Also fixed broken nav expand/collapse: supplemental footer-content.hbs was loading site.js again after Valentus footer-scripts already did, which registered toggle handlers twice so chevrons appeared dead. Removed the duplicate script tag.