DAMASCUS, Syria — Handcuffed and squatting on the floor, Abdullah Zahra saw smoke rising from his cellmate’s flesh as his torturers gave him electric shocks. Then it was Zahra’s turn. They hanged the 20-year-old university student from his wrists until his toes barely touched the floor and electrocuted and beat him for two hours. They made his father watch and taunted him about his son’s torment. That was 2012, and the entire security apparatus of Syria’s then-President Bashar Assad was