The robotics pioneer who helped unleash the Roomba vacuum is now betting that you might one day replace your beloved dog or cat with a plush robot that follows you around your home and adapts to your daily habits. Colin Angle unveiled a four-legged prototype of that artificial pet, called the Familiar, on Monday. Imagine a creature the size of a bulldog with doe-like eyes and bear cub ears and paws, extending itself into a greeting stretch that invites you to pat its touch-sensitive fake fur. “We chose a form factor that’s not a human, not a dog, not a cat, because we wanted to steer away from all of those preconceptions,” said Angle, who leads the startup Familiar Machines & Magic and before that was longtime CEO of Roomba maker iRobot. This kind of lifelike machine — powered by the latest artificial intelligence technology — would not have been possible when Angle co-founded iRobot in 1990 or launched the first Roomba in 2002. It's hardly the first effort to build a pet-like household robot.…