- Reset `hi` on Escape and gate `activeOptionId` on `open`, so a dismissed
panel never exposes an aria-activedescendant pointing at an unmounted option,
and no stale highlight flashes on reopen (live-verified: aria-activedescendant
is null when nothing is highlighted / the panel is closed).
- Strengthen the reopen test: setQ now writes back to the mock provider's q, so
the test asserts a FRESH suggest query fires on retype (q="matrixx"), not just
that a cached listbox re-appears.
- Add a combobox-ARIA test: role=combobox, aria-expanded toggles with the panel,
and aria-controls associates the input with the listbox it opens.
Suite 171 green; typecheck + eslint clean.