/// The `search` clause on a `find` query: an optional lexical (BM25) query and/or fuzzy query.
///
/// The query engine treats this as a membership + relevance annotation only — it computes no
/// scores itself. The caller resolves the spec into a [`crate::query::QueryScores`] (BM25 / fuzzy
/// live in the `diwe` engine crate) and injects it via `execute_with_scores`.