vash-codex/servo-facial-tracking ? reverse-engineered prompt

Build me a small app that lets a webcam track a face and physically turn a servo so it follows that person left and right.

I want a simple Python interface where I can collect face samples, train the model, choose the serial port, and start or pause tracking. It should use OpenCV for face detection, and it should be able to work with face recognition so it follows the trained person, but also still do basic tracking without recognition if needed. Please include smooth servo movement, manual keyboard controls for centering and nudging left or right, and an easy way to invert direction if the servo moves the wrong way.

Also include the Arduino sketch that listens over serial at 9600 baud and drives the servo on pin D9. Make it easy to set up, with clear instructions for training, wiring, and running the whole thing. If you need to check current docs for OpenCV or serial handling, go ahead and look them up.