Meta went from App Store #57 to #5 in four days after launching Muse Spark. The way they did it tells you everything about what the model actually is. When you download the Meta AI app, Instagram sends notifications to your friends telling them you're using it. No opt-in prompt. No toggle. Your friends get a notification as prominent as a new follower, and suddenly everyone in your social graph knows you're chatting with an AI. One TechCrunch writer called it a personal humiliation. Meta calls…