NBC yesterday laid off the nonwriting staff members of its two late-night entertainment shows, the “Tonight Show With Jay Leno” and “Late Night with Conan O’Brien,” because of the strike by Hollywood scriptwriters. The move had been expected after NBC executives declined to extend the period where the network had been paying the nonwriting employees of the shows. Mr. O’Brien has said he will pay the salaries of his staff for at least next week. Mr. Leno has not made a similar announcement, though a representative said this week that Mr. Leno was paying a Christmas bonus to staff members....