The over-scroll class keeps recurring (last instance fixed in the
settings shell): a page-level viewport-height reserve or bottom gutter
inside the scrolling main stacks on the shell-owned padding and the
page scrolls past the last card into an empty band. Pin the invariant
instead of the instance: across the settings routes (short hub, long
sortable-list subpages, long form section) at desktop and phone
viewports, main.scrollHeight must stay within the last content
element's bottom edge plus the shell-owned padding and a small
tolerance. Descendants of nested max-h scroll containers are excluded
from the content measure — their overflow never contributes page
scroll height.
