W ASHINGTON — A union for U.S. Agency for International Development contractors asked a federal judge Tuesday to intervene in any destruction of classified documents after an email ordered staffers to help burn and shred agency records. Judge Carl Nichols set a Wednesday morning deadline for the plaintiffs and the government to brief him on the issue. A person familiar with the email who spoke on the condition of anonymity for fear of reprisal verified that it was sent to at least some