USR369 reported HTML pages were not being kept up / Builder not doing maintenance checks -- no recurring duty or SOP existed for this specifically. Before building anything, checked whether the existing maintenance-schedule-api.php system (built earlier today per FIX-LOG, initially misjudged as missing until I searched the correct path backend/standards/system/ + backend/api/critical/ instead of backend/tools/) already covered it -- confirmed it did not; its 6 existing duties (health-check, taskgate-review, housekeeping-sweep, backup-naming-audit, snapshot-rotation, masterlist-verify) have no HTML page check. Added a 7th duty (html-page-check, weekly, owner Builder[20]) via the existing add_duty/update_duty actions rather than building a parallel system. Wrote SOP-HTML-PAGE-MAINTENANCE.md defining the actual check (inventory match / staleness / loads clean / JS syntax), registered in SOP-INDEX.md, broadcast (95). Flagged a real blocker in the SOP itself: page-inventory.html (the file this check needs as ground truth) is currently 404 -- Builder[20]'s first run needs to rebuild it first.