Open-state of the root popover. When provided, a settled hover intent
opens only while the root menu is open: a dwell timer can outlive a
dismissal (hidden elements do not reliably fire pointerleave), and its
late true edge must not show an orphaned submenu popover. The edge is
still consumed, so reopening the root never retroactively opens a
submenu from a stale dwell. Close edges route regardless - closing is
always safe. Absent: opens are not gated.