A 54-year-old woman has jaundice and generalized pruritus that keeps her awake at night. On examination, her liver span by percussion in the midclavicular line is 17 cm. There is no splenomegaly. Serum alkaline phosphatase is 350 U/L (N 40 to 129 U/L), ALT 75 U/L (N 7-50 IU/L), AST 100 U/L (N 8 to 48 IU/L), total bilirubin 7 mg/dL (N 0.3 to 1.9 mg/dL), and direct bilirubin 6 mg/dL (N 0 to 0.3 mg/dL). Which of the following is the most likely diagnosis?