/**
 * Formats a date string as a relative time (e.g., "5m ago", "2h ago", "yesterday").
 */
export function timeAgo(dateStr: string): string {
  const diffMs = Date.now() - new Date(dateStr).getTime()
  const minutes = Math.floor(diffMs / 60000)
  if (minutes < 1) return 'just now'
  if (minutes < 60) return `${minutes}m ago`
  const hours = Math.floor(minutes / 60)
  if (hours < 24) return `${hours}h ago`
  const days = Math.floor(hours / 24)
  if (days === 1) return 'yesterday'
  return `${days}d ago`
}