If I unintentionally omitted mentioning the time period for the temporary marriage contract, does it automatically become permanent or does my intention play a role in determining its duration?
If the time period was not mentioned in the contract, it becomes permanent according to many scholars, that is why you need to recite Talaq in front of two pious witnesses when she is not in her menses to terminate that contract. After that divorce, you both can read a temporary marriage mentioning the Mahr and period.
Wassalam.