The grappling gun of “Batman Begins” seems like trendy tactical tech, with pains taken to make it seem like a thing that could exist in real life, while Ben Affleck’s grappling gun in “Batman v Superman” is needlessly bulky. The grappling gun in “The Batman” snaps out from Batman’s arm, a la Travis Bickle’s gun sleeve in “Taxi Driver,” a key affect on the film as a complete. When Batman needs to scale a constructing, make a quick but mysterious exit, or snare a goon by the throat, the grappling gun is there for him. Like his gauntlets, Batman’s cape …