A 68-year-old man presents to clinic after an incidental ECG shows atrial fibrillation. He has hypertension and type 2 diabetes; eGFR is 72 mL/min/1.73 m², platelets 230,000/µL. His CHA₂DS₂-VASc score is 3 (age 65-74 = 1, HTN = 1, DM = 1). He has no history of valve disease or prior bleeding. What is the most appropriate next step to reduce stroke risk?