/** Parses a numeric route param (e.g. /admin/posts/[id]); null when invalid. */
export function parseIdParam(raw: string): number | null {
  if (!/^\d+$/.test(raw)) return null;
  const id = Number.parseInt(raw, 10);
  return Number.isSafeInteger(id) && id > 0 ? id : null;
}