A 38-year-old woman with HIV-1 infection on a stable ART regimen (dolutegravir + tenofovir/lamivudine for 18 months) presents with a 2-week history of nausea, vomiting, and right upper quadrant pain. Liver function tests show AST 280 U/L, ALT 320 U/L, ALP 180 U/L, and bilirubin 2.8 mg/dL. Viral load is undetectable (< 50 copies/mL) and CD4 count is 680 cells/μL. Hepatitis B and C serology are negative. Abdominal ultrasound is normal. What is the next step in management?