- optional IndexDropper reports whether a dropped index existed; DropIndex falls back to Flush
- optional IndexEnsurer creates an empty index from its schema; EnsureIndex is a no-op otherwise
- typesense implements both (404 is already absent; ensure reuses collection creation)
- optional beachcomber.PageSearcher returns a page of candidate ids plus
the engine's found count; beachcomber.SearchPage falls back to
SearchIDs for engines without it, so Engine is unchanged
- Query.QueryByWeights is sent to Typesense as query_by_weights; a
mismatched weight list or a page above typesense.MaxPerPage (250) is
refused before any request