A Partnership Forged To Thwart Terrorism
Article discusses alliance forged between Atty Gen John Ashcroft and FBI Director Robert Mueller, and notes it is departure from past relationships of people in these posts; FBI has ceded much of its traditional independence to Justice Dept, with Ashcroft taking command of investigation as he defers to Mueller on strategic decisions; some in bureau welcome change as indication that fight against terrorism is more important than turf battle, while others perceive stronger loyalty to Ashcroft than bureau; photos (M)