A 66-year-old man is newly diagnosed with non-valvular atrial fibrillation detected incidentally on ECG during a pre-operative assessment. He has well-controlled hypertension but no heart failure, diabetes, prior stroke, or vascular disease. He is otherwise fit, with normal renal function and no contraindications to anticoagulation. According to the CCS CHADS-65 algorithm, what is the most appropriate antithrombotic strategy for stroke prevention?