SAN FRANCISCO — Baseball has the minor leagues. Medicine offers residency programs. But recent law school graduates have no equivalent training opportunities to hone their skills — at least until now.A tight job market for new lawyers and a push to make legal representation more affordable have prompted law schools in California and other states to fund startup law firms.About two dozen so-called legal incubators or fellowship programs have cropped up nationwide in recent years to teach a few select law graduates the …