Is it narrated that the Imam should stand slightly in front of the worshipper when two men pray in congregation?

There is no evidence that the Imam should stand slightly in front of a single follower. The apparent ruling is that the follower should stand to his right, aligned with him. The Prophet (peace be upon him) took Ibn Abbas by the head and placed him to his right. The Imam and the follower are considered a single row, and rows are commanded to be straightened. Standing ahead or behind contradicts this straightening.