`--database` and `--db` read as one word abbreviated but take different
things, a configured name against a filesystem path, and they sit in
different positions: `haiku-rag --db /path info` fails with `No such option`.
The CLI already says "database" to the user everywhere it prints one, so the
name it selects by should say the same. Unreleased, so no deprecation.
Also: without a reranker, raise `search.limit` with the number of databases
searched, since each contributes its best matches to a list truncated back
to the limit.
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