dsh-markdown-preview: Inline preview of produced files in DSH Web

dsh-markdown-preview is a community plugin for DeepSeek Harness Web (v0.3.0, MIT license) designed to optimize the preview experience of agent-generated files. By intercepting default click behaviors, it supports directly previewing Markdown, code, images, and plain text within the chat window, eliminating the need to open native applications or new tabs and significantly reducing viewing costs. Core features include server-side high-quality rendering and syntax highlighting using `markdown-it` and `highlight.js`, support for 40+ code extensions and multiple image formats, and interactions such as full-screen, copy, and collapse, with perfect adaptation to light and dark themes. The plugin preserves the original file line experience without affecting other functions. Installation requires DSH version 0.1.0-rc or later.