export interface MigrationResult {
    /** Whether the migrator ran (false when marker present or no work to do). */
    ran: boolean;
    /** Files successfully moved. */
    moved: string[];
    /** Files that failed to move along with the error message. */
    failures: Array<{
        from: string;
        to: string;
        error: string;
    }>;
    /** Whether the idempotency marker was written this run. */
    markerWritten: boolean;
}
export interface MigrateOptions {
    /** Sink for one-line-per-file progress messages. Defaults to console.error. */
    log?: (line: string) => void;
}
/**
 * Run the migrator once. Returns details of what happened so callers
 * (tests, debug logging) can assert behavior; production callers may
 * safely ignore the return value.
 */
export declare function migrateLegacyData(opts?: MigrateOptions): MigrationResult;