nilaoda/BBDown ? reverse-engineered prompt

Build me a simple command line tool for downloading videos from Bilibili.

I want it to feel easy to use from a terminal, with clear prompts or arguments for pasting a video link, choosing quality, and saving the file locally. It should handle the common stuff a downloader needs, like showing progress, naming files sensibly, and giving helpful errors when something goes wrong. If there are separate audio and video streams, combine them into one playable file. If there are multiple episodes or parts, let me download them one by one or in a batch.

Keep the interface clean and straightforward, and make sure it works well on Windows too. If you need to check current Bilibili or .NET docs online while building it, go ahead. Also include a short README with basic usage examples and a note that people should use it responsibly and follow the site rules and copyright laws.