A 32-year-old woman with secondary infertility (1 year of unprotected intercourse) and anovulation is being considered for ovulation induction. Her BMI is 24 kg/m², baseline FSH is 6 mIU/mL, and transvaginal ultrasound shows normal ovaries without polycystic morphology. Which is the most common first-line agent used for ovulation induction in this patient?