Lawyers for an American believed to be held by the Taliban for nearly two years are asking a United Nations human rights investigator to intervene, citing what they say is cruel and inhumane treatment.Ryan Corbett was abducted Aug. 10, 2022, after returning to Afghanistan, where he and his family had been living at the time of the collapse of the U.S.-backed government there a year earlier. He arrived on a valid 12-month visa to pay…