Firefighters, medics and FBI agents swarmed a normally quiet stretch of the Alameda waterfront next to the USS Hornet Museum on Wednesday morning, maneuvering around people lying on the ground as an ominous orange smoke filled the air and brightly colored emergency vehicles crowded the road. The alarming scene was part of a two-day exercise called “Operation Seasick” — six months in the making and organized by the FBI — to practice how local, state and federal law-enforcement agencies and emergency responders would work together in the event of a complex terror attack involving weapons of mass destruction in an area like the Port of Oakland.