hide() did not invalidate in-flight search requests. Clearing
the input or picking a contact while a request was pending let
the old response re-render and pop the suggestion list back
open. Bump requestSeq in hide() so every dismissal retires
pending responses.
Add a Vitest + jsdom harness with black-box tests for the
invitee widget, covering the stale-response race both on
field clear and on contact pick.
