When you think of modern spy movies, you probably picture big-budget action, impossible stunts, and a CGI-enhanced world of espionage. But “Black Bag” does something rare: it keeps things grounded, proving you don’t need explosions to make a spy film gripping. Steven Soderbergh’s latest thriller is a masterclass in slow-burn tension, with sharp dialogue, powerhouse performances, and a focus that’s less on government secrets and more on the secrets between two people in a marriage. A Marriage Disguised as a Spy Story At its core, “Black Bag” is really about trust, and not just in the professional, intelligence-agency sense. The…