Disney’s “ Tron: Ares ” will light up the top of the box office in its debut, though the sci-fi entry is coming in dimmer than its projections. Meanwhile, the Channing Tatum caper “ Roofman ” looks headed for a second place bow. The “Tron” threequel earned $14.3 million across Friday and previews from 4,000 venues (that includes early access screenings on Wednesday ahead of the wider traditional Thursday rollout.) Pre-weekend tracking had forecast a debut north of $45 million — a range that’s