A day after China sweetened a much criticized U.S. trade deal with a promise to reopen dialogue over its dismal human-rights policies, the Chinese government detained a leading dissident and veteran of the 1989 Tiananmen Square protest. Police took the dissident, Wang Dan, from his home for questioning but released him seven hours later. That's the second time he's been detained since U.S. Commerce Secretary Ron Brown arrived Saturday for a Beijing visit. Brown had declared yesterday's offer a vindication of the U.S. decision to stop threatening to link China's most-favored-nation trade status and human rights. Today, State Department officials said they were "distressed."