dsh-video-downloader: Media recognition and download tool for DeepSeek Harness

`dsh-video-downloader` is a media download plugin for DeepSeek Harness, maintained by zimai233 and licensed under the MIT License. It provides media URL recognition and processing functions tailored for agents, supporting sites such as Bilibili, YouTube, Douyin, and Xiaohongshu. This plugin is a pure ESM package with zero build steps; its core logic is exported as pure functions, facilitating testing and secondary development. It offers three core tools: `video_analyze`, which only analyzes the URL and returns whether it is a media file, the site, quality, extension, and MIME type hint; and `video_download`, which uses browser-style request headers to stream and save media locally. It supports custom paths and headers, and includes features for following redirects, handling timeouts, and cancellation.