Among the sports celebrities of 1977 were schoolboys and girls, a ninth-grader who was the toast of Forest Hills, an 8-year-old who made Frank Shorter blink, a playground star who led grown men a merry dance. Their wondrous skills delighted all who watched, and brought refreshment and a certain joy to big-time athletics. But of all the prodigies, none burst on the scene so remarkably or garnered as much glory as Steve Cauthen, 17, who just 12 months ago was a bug boy at a bush track and now is Sportsman of the Year.