DeepSeek Harness File Preview and Editing Plugin

`dsh-preview-ui` is a browser extension designed to improve development efficiency within the DSH environment. It integrates file tree browsing, multi-format preview (supporting code, Markdown, images, PDF, Office files, and more), and online editing, while also providing version management and full-text search capabilities. Users can use it through drag-and-drop or Agent tools, with support for securely editing text files in the browser and automatically saving snapshots, enabling one-stop code management.