dsh-media-preview: Audio and Video Preview Plugin for dsh-better-sidebar

dsh-media-preview is a plugin for the DeepSeek Harness (DSH) web GUI designed to address the pain point of requiring external players when browsing audio and video files in the sidebar. Registered as a FileViewer within dsh-better-sidebar, this plugin supports inline playback of audio and video files using native browser controls. Its core capabilities include providing a standalone streaming route at `/media-preview/file`, supporting HTTP Range (206) seeking to optimize the scrubbing experience for long videos, and utilizing streaming responses to avoid buffering the entire file. File recognition supports extension matching and magic-byte sniffing (e.g., MP4, MP3, FLAC), and includes a built-in loopback trust boundary.