When Chrissie Evert retired last fall, tennis suffered a large net loss in charm. But suddenly the women's tour has a new advantage in. Juniors champ JENNIFER CAPRIATI went trick-or-treating last Halloween, but she is such a demon on the court that organizers bent their rules to let her turn pro three weeks shy of her 14th birthday, March 29. The Wesley Chapel, Fla., ace enters the big time with a $3 million sportswear contract, a wicked forehand and a smile to beguile all but those across the net.