dsh-asset-library: DeepSeek Harness Local Asset Library Plugin

`dsh-asset-library` is a local media asset management plugin for DeepSeek Harness. It converts images, videos, and audio files in project directories into a browsable and annotatable asset panel, and provides Agent tools for semantic search and bulk path retrieval. The plugin features grid view, tag management, batch operations, and secure permission controls, without relying on ffmpeg, making it suitable for unified management of local media assets in DeepSeek Harness.