KABUL — A series of errors, human and technical, led to an American gunship bombing a Doctors Without Borders hospital in the northern Afghan city of Kunduz last month, killing 30, a U.S. military probe has concluded. Several American personnel, most likely pilots and U.S. special operations soldiers, who made the decision that led to one of the deadliest incidents of civilian casualties of the war, have been suspended and could face further disciplinary action, senior U.S.