A man walks into a diner, wearing a clear plastic raincoat, mismatched shoes and what looks like a suicide vest. He claims to be from the future, sent back in time to save humanity from the imminent and inevitable AI uprising. This disheveled evangelist is played by Sam Rockwell in the wild-eyed “is he deranged or is he the only sane one here?” mode of many a Terry Gilliam character (think Robin Williams in “The Fisher King” or Bruce Willis in “12 Monkeys”). He’s a bum-prophet — the kind who