The Directors Guild of America has secured a provision in its new contract that limits actors on TV series from directing episodes, as it seeks to preserve jobs for career TV directors. The provision is meant to address the 40% downturn in production jobs over the last four years, which has left a great many of the union’s 19,500 members out of work. The DGA reached its tentative agreement with the Alliance of Motion Picture and Television Producers on Tuesday. The terms — released on Friday —