While the world's most famous automakers were pulling the covers off their latest, shiniest offerings at the Los Angeles Auto Show, a dark gray sedan circled the convention center, almost silently. Riding on 21-inch wheels, the Lucid Air cuts a muscular stance, its door handles flush with the body of the car, one thin bar of light bars stretching across its front, another along the slightly boxy rear. Fully electric, it offers a tempting vision of the future.