`resolve_citations` documented the behaviour it now rejects: a shared chunk id
resolving to whichever result came last.
The storage page ran two embedding checks together as if the second explained
the first. They are separate: each database against the configuration on open,
and the databases in a selection against each other, which raises in read-only
mode too and does not apply to full-text search.
`several` becomes `multiple` where it names the feature, matching the docs and
`covers_multiple`.