{% comment %}
Vertical nav for sidebars. The container styles its item links via descendant
selectors (keyed on the `.is-current` marker the item adds when current), so
items stay structural.
- default: filled active rows
- variant="sidebar": accent left-bar rail (continuous, no row gap)
When `persist_scroll` is set and the navlist is its own scroll container
(give it a max-height plus overflow-y-auto), it remembers its scroll position
across full page loads via sessionStorage, keyed on `scroll_key`. It only restores
that position when you navigated via a link inside this navlist, so arriving from an
unrelated page (a top nav, an external link) starts at the top rather than resuming a
stale position. Useful for long sidebars so the list does not jump to the top on every
in-nav navigation.
{% endcomment %}