import type { Stringer } from "./api.js" ; example ```ts
 * hstr("abc")  // "3Habc"
 * hstr(123.45) // "6H123.45"
 * hstr("")     // "0H"
 * hstr(null)   // ""
 * ```
 *
 *  https param x export const hstr = ( x ) => x != null ? ( ( x = x . toString ( ) ) , `${ x . length }H${ x }` ) : "" ;