LONDON — As the suspected source for the biggest intelligence leak in American history faces his first hearing Friday, U.S. prosecutors have their eye on another prize: the man who disclosed the documents to the world.When WikiLeaks' spectacular disclosures of U.S. secrets exploded onto the scene last year, much of Washington's anger coalesced around Julian Assange, the silver-haired globe-trotting figure whose outspoken defiance of the Pentagon and the State Department riled politicians on both sides of the aisle.