WASHINGTON, July 1 - For nearly two years, the investigation into the leak of a covert C.I.A. officer's name has unfolded clamorously in the nation's capital, with partisan brawling on talk shows, prosecutors interviewing President Bush and top White House officials, and the imminent prospect that reporters could go to jail for contempt of court. But the woman at the center of it all, Valerie E. Wilson, has kept her silence, showing the discipline and discretion that colleagues say made her a good spy. As her husband, Joseph C. Wilson IV, has become a highly visible critic of the administration...