SARATOGA SPRINGS, N.Y. — Even as he closes in on becoming the 18th jockey to reach the 6,000-win milestone, even as he nears his 49th birthday in late October, Javier Castellano sees no end to his Hall of Fame career. He points to the examples of Mike Smith and John Velazquez. Smith, 61, rides far fewer horses than he once did but remains formidable. Saratoga handicappers know to look long and hard at anything Johnny V rides. He still has it at …