A 42-year-old woman with chronic kidney disease (eGFR 25 mL/min) presents with polyuria and polydipsia. Her serum sodium is 152 mEq/L, serum osmolality is 310 mOsm/kg, and urine osmolality is 180 mOsm/kg despite elevated serum osmolality. Which is the most common cause of her diabetes insipidus?