A 36-year-old right-handed woman sees a neurologist for persistent pain in her right forearm and hand, not relieved by naproxen or a wrist brace. She experiences aching pain aggravated by use and numbness in her thumb and fingers, worse during work as an assembly-line worker. She's otherwise healthy, takes an oral contraceptive, had an appendectomy, and is married with two children; her husband works in accounting.  The patient has normal vital signs and a BMI of 28. She has normal range of motion and muscle strength in both arms but perceives weakness in her right arm. Sensation to light touch is reduced on the palmar aspect of the thumb, index finger, and middle finger of the right hand. Tinel signs are negative over the peripheral nerves, except tapping over the medial forearm just distal to the elbow causes mild paresthesia in the thumb and index finger on the right side only. Radiographs of the elbow, forearm, and wrist are normal, as are the results of routine blood tests. Which of the following diagnoses is most likely,