The ingester manufactured `data_dir / haiku.rag.lancedb` whenever `--db` was
absent and passed it to HaikuRAG. A path is now an explicit override that
clears the configured URI, so a `lancedb.uri` deployment wrote to local disk
while the control plane reported on the remote.
`IngesterApp` resolves the databases it works on once, in its constructor, and
both the client it opens and the control plane read that scope. `--db` names
one directly and nothing stands in for it, so a configured set is refused
rather than guessed, and `AmbiguousDatabaseError` joins the errors `cli()`
turns into a clean exit.
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