Synthesia just put an AI avatar on the other side of the video call. It runs the conversation, pushes back on your answers, and scores you when it's done. The company is worth $4B, counts 90% of the Fortune 100 as customers, and this is its move from selling training videos to holding the meetings themselves. Run the math on the sales rep claim. A human trainer roleplaying 1,000 reps for 30 minutes each needs 500 hours of sessions. That's three straight months of doing nothing else. The avatar…