The screenwriter Aaron Sorkin makes his directorial debut with “Molly’s Game,” and it’s a promising one at that. Swift, stylish, tough-minded and sharp-tongued, this engaging fact-based drama, about a young woman who at one point ran the richest poker game in the world, is worth recommending if only to see its star, Jessica Chastain, at the top of her nerviest, most icily self-controlled game. Chastain plays Molly Bloom, who despite her fictional-sounding name was a real-life woman who was a highly ranked competitive skier before she moved to Los Angeles in the early 2000s.