zyipeng/video-downloader ? reverse-engineered prompt

Build me a simple AI assistant skill that can download videos from YouTube, Bilibili, Douyin, Xiaohongshu, Kuaishou, Weibo, X, Vimeo, and TikTok into my local Downloads folder.

I want it to feel easy for a normal person to use, where I just paste a link, the assistant figures out what site it is, shows me the available quality choices, and then downloads the one I pick. Please make it smart about choosing the best format for quality, speed, or compatibility, and make sure the output plays nicely on common devices and apps when I choose the compatible option.

It should handle the tricky sites too, especially Douyin and Kuaishou, and use browser cookies when needed without making me repeat setup every time. Keep it working as a reusable skill with a few shell scripts and a clear setup guide. If you need to check current docs for tools like yt dlp or aria2, go ahead and look them up online.