```ts
/** Truncate text to limit characters with ellipsis if longer. */
export function truncate(text: string, limit: number): string {
  if (!Number.isInteger(limit) || limit < 3) {
    throw new Error('limit must be an integer of at least 3');
  }
  if (text.length <= limit) return text;
  return text.slice(0, limit - 3) + '...';
}
```