QALANDIA: In the crowded Qalandia refugee camp, UNRWA’s training center is an island of calm where young people from the occupied West Bank master trades, but a recent Israeli ban on all cooperation with the UN agency has left the center in limbo. On the spacious campus, a stone’s throw from the wall that separates the West Bank and Israel, plumbers in training assemble pipes, future electricians wire circuits, and carpenters hammer together roof frames.