The Hidden detail sections disclosure kept its expanded state after the
last section was restored and across provider switches, so the next
hidden section reappeared with its restore list already open. The list
now starts collapsed for each provider and collapses when nothing is
hidden. The popup-hidden-sections smoke scenario asserts both cases.

Co-authored-by: Claude Opus 5.5 (1M context) <noreply@anthropic.com>