Dark83Duck/video-downloader ? reverse-engineered prompt

Build me a simple video downloader tool that works from the command line and can also be used as a skill or plugin for AI assistants like Claude Code and Codex.

I want to paste a YouTube link and have it download the video in a format I choose, with options for best quality or specific resolutions like 1080p, 720p, 480p, 360p, or worst. It should save as MP4 by default, but also support WebM and MKV. I also want an easy audio only mode that pulls out the sound as an MP3.

Please make it smart enough to check for missing dependencies like yt dlp and install what it needs, and use ffmpeg when available for merging and audio extraction. The script should let me choose an output folder too, and it should be easy to run directly from the terminal without needing an agent. If you need to check the latest docs for the tools, go ahead and look them up online.