A 38-year-old right-handed carpenter from Delhi presents with a 3-week history of progressive weakness and wasting of the thenar eminence. He reports pain and paresthesias in the lateral three and a half fingers of the right hand, worse at night. Examination reveals loss of thumb opposition and abduction, and sensory loss over the lateral palm and dorsal aspects of the index and middle fingers. Tinel's sign is positive at the wrist. Which nerve is compressed, and at what anatomical location?