The Big Ten Conference banned Jim Harbaugh from coaching at Michigan’s three remaining regular-season games Friday, escalating an extraordinary confrontation with college football’s winningest program about a sign-stealing scheme that has rocked the sport. The school delivered on its promise to fight back in court a few hours later, asking a Michigan judge for a temporary restraining order that would allow Harbaugh to coach the Wolverines in their biggest game of the season so far.