A 68-year-old man presents to the emergency department with 3 hours of central chest pressure radiating to his left arm. ECG shows ST-segment depression in leads V4-V6 and elevated high-sensitivity troponin. Blood pressure is 132/80 mm Hg and oxygen saturation is 97 percent on room air. Coronary angiography is planned within 24 hours. What is the most appropriate immediate antiplatelet strategy?