What is the ruling on semen exiting during sexual intercourse at the time of the Fajr اذان for a woman who is fasting to make up for missed days, and does that invalidate the fast?

Making up a missed fast (qadaa') is valid if intercourse occurs before the Fajr adhan. However, if the adhan for Fajr occurs at the break of dawn and intercourse continues, then the fast is invalid, and it becomes obligatory to make up another day without expiation (kaffarah). There is no obligation to complete the corrupted day.