/** Trimmed string, or null when absent/empty. */
export declare function normalizeStoredString(value: unknown): string | null;
/**
 * Firestore Timestamp-like -> ISO 8601, or null. Accepts only objects exposing
 * `toDate()`. A raw `Date` is deliberately NOT accepted: that matches both call
 * sites this replaced. `message.ts` keeps its own
 * Date-tolerant normalizers — a different contract, not this one.
 */
export declare function firestoreTimestampToISOString(value: unknown): string | null;