A 56-year-old man undergoes a low anterior resection after neoadjuvant chemoradiation for a T3N0M0 rectal cancer located 9 cm from the anal verge. Eight days later, he presents to the emergency department with mild abdominal pain and a temperature of 102.2°F (39°C). Laboratory results are significant for a white blood cell count of 14,000/µL (14×10⁹/L). Computed tomography of the abdomen and pelvis shows pneumoperitoneum with contrast extravasation into the pelvis. Abdominal examination shows focal peritonitis in the left lower quadrant. Intraoperative findings demonstrate a 3-mm anastomotic disruption anteriorly. In addition to abdominal washout, what is the best surgical option for this patient?