JENIN, West Bank — When Israeli snipers took positions in her neighborhood, Haleemeh Zawaydeh knew her family needed to leave quickly. As the snipers' gunfire rang out, the 63-year-old matriarch said there was no time to pack as she and 14 other family members fled on foot. The invasion of Jenin was faster than past Israeli assaults, she said. And, now, like some 37,000 other Palestinians the U.N. estimates have been driven out by a month-old offensive against militant groups in the occupied