The nameplate above the corner locker at the far end of the Red Sox' clubhouse was gone before the end of yesterday's game. And now, so is Kevin Youkilis. A trade that had become inevitable over the past few weeks has turned into a reality. The Red Sox sent their hard-nosed corner infielder, one of the last links to the 2004 World Series champs, to the Chicago White Sox for utilityman Brent Lillibridge and Triple-A right-hander Zach Stewart. The Red Sox also agreed to pay $5.5 million of the nearly $7 million remaining on Youkilis' contract.