cramatsu/blurryface ? reverse-engineered prompt

Build me a simple Python command line tool that takes an image file and automatically blurs out any faces it finds for privacy.

I want it to use a YOLO based face detection model, then apply a Gaussian blur to each detected face. It should work from the terminal with a command like blurryface path/to/image.jpg and support a few options so I can tune the results, like confidence threshold, IoU threshold, and blur radius. Please make the defaults sensible, but let me override them if the detector misses faces or catches too much.

Use Poetry for setup and dependency management, and make sure the project is easy to install and run from the README instructions. If there are any model or image processing details you need to confirm, look up the current docs online if needed. I mainly want a clean, working first version that can process a photo and save the blurred result without making me deal with extra complexity.