application.Window carries unexported methods, so the hide/restore paths could
not be faked and the earlier tests could only assert which entries survived a
restore, never which windows were actually shown.
The bookkeeping now goes through hideableWindow, the four methods it needs,
with the window enumeration and the main-window raise behind seams that are nil
in production. That makes the case the owner tag exists for testable end to
end: an install started during SSO login restores only the login popup it hid,
and leaves the main window hidden until the login popup itself closes.
Windows hidden while a popup owned the screen went into one untagged list, so
whichever popup closed first restored all of them and emptied the list. An
install started during SSO login re-showed the main window the login popup had
deliberately hidden, and left the login popup with nothing to restore.
Each entry now records the popup that hid it, and a restore releases only that
popup's own entries. This also subsumes the manual filtering CloseRenewFlow did
to keep its own session-expiration window from being re-shown.