/** Quote a user query for FTS5 phrase/prefix-safe matching. */
export declare function escapeFts5Query(raw: string): string;
/** Build a syntax-safe, recall-oriented query for natural-language memory search. */
export declare function buildFts5SearchQuery(raw: string): string;
/** Normalize FTS5 BM25 ranks, where a more-negative rank is a better match. */
export declare function fts5RankToScore(rank: number, bestRank: number, worstRank: number): number;
/** Bounded lexical fallback for reformulations unsupported by unicode61 tokenization. */
export declare function memoryLexicalSimilarity(query: string, content: string): number;
/** Local deterministic embedding used to complement FTS without network or model coupling. */
export declare function memoryVectorSimilarity(query: string, content: string): number;