What does yutto do?
Execute end-to-end Bilibili downloads with yutto. Use this whenever the user wants you to actually download a Bilibili uploaded video, series, course, favorites, watch later, collection, playlist, or audio for them, or wants you to install/configure yutto and complete the download instead of merely explaining commands. This skill should verify installation and FFmpeg, check auth status, collect missing required inputs such as the link and download directory, then run the download.