dsh-vidfetch: Enabling Video Downloads for DeepSeek Harness Agents

DSH-vidfetch is a DeepSeek Harness (DSH) plugin that enables agents to directly download videos from URLs without developer intervention. By registering a `fetch_video` tool and leveraging yt-dlp, it automatically retrieves the best available audio and video streams and saves them to a specified directory, supporting zero-configuration installation and use. When using the plugin, ensure proper outbound network permissions, file system write permissions, and security safeguards, and avoid passing untrusted videos into execution pipelines.