<pagination-nav>

Minimal, controlled pager for list/table views: a previous/next control pair
around a "Page N of M" status. It owns no data — the consumer sets
current-page / total-pages and moves the page in response to the
page-change event (typically alongside its own data fetch), exactly like
data-table leaves the row data to the caller.

Previous is disabled on the first page and next on the last; neither fires an
event when there is nowhere to go.

The prev/next buttons are treated as ui-button's secondary variant:
they read the same shared --ui-button-secondary-*/--ui-button-highlight
tokens (and --ui-button-secondary-surface-muted for hover, since — like
button-group's unchecked segments — they already paint
--ui-surface-muted on hover by default), so a gradient theme applies
consistently here too.