Chen Guangcheng, the blind Chinese dissident who fled house arrest last month in a dramatic escape from security forces, left the American Embassy in Beijing on Wednesday after securing assurances from the Chinese government that he would remain safe, American officials said in the first account of his diplomatically tense six-day stay there. The officials described details of the negotiations between both governments and Mr. Chen as well as a telephone call to the dissident from Secretary of State Hillary Rodham Clinton after he left the embassy compound for treatment at a medical facility here. Mrs. Clinton said in a...