`HaikuRAG.__init__` said an omitted `db_path` uses `storage.data_dir`, which
is the last of three; and that `sources` is ignored for a single `uri`, where
it raises, since only `lancedb.databases` names databases.
The name is not the only identity leaving the configuration: results,
citations, model input and errors opening a named database carry it, while
`info`, `init` and `tag` print the location. `sources=[]` returns no search
results, but `ask` and `analyze` still answer, without evidence.
Trim the comments that still narrated a failure or an alternative to the
invariant they were there for.
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