What are the consequences for the Imam and the congregants if the Imam deliberately laughs in the first rak'ah of Friday prayer, according to the school of Imam Malik?

The Imam and the congregants must stop the prayer and repeat it if the Imam laughed intentionally, because intentional laughter invalidates the prayer. The Imam should not appoint a successor if he is the one who laughed. Maliki jurists held that prayer is invalidated by loud laughter (qahqahah) absolutely, whether it was intentional, accidental, or involuntary. So, if the Imam laughed loudly, his prayer is invalidated, and the prayer of the congregants behind him is severed. The Imam must repent to Allah if he intentionally laughed during his prayer.