What a read says before it has an answer, wherever rows or a value are not
the thing to draw. Each draws one paragraph on the application's own status
slot: the words are the caller's, the role and aria-busy are not
negotiable. ListView and DetailView draw these for their own states.
Busy text said only once the wait is noticeable: a read that answers
quickly shows nothing, where a "Loading…" drawn for a frame read as a
flash. Attach it to the status slot. The paragraph itself always renders,
so its space is held from the start and nothing moves when the text
shows; answering in time removes aria-busy before the delay ends, so
the text never appears. No spinner art: the text and this delayed fade
are the whole convention.