dsh-md-preview: DSH's Markdown right-side preview plugin

dsh-md-preview is an MIT-licensed plugin for DeepSeek Harness (DSH) designed to address the issue of viewing `.md` files in Web sessions requiring a context switch. The plugin supports side-by-side Markdown previews in the right sidebar, with top alignment and adjustable width. It also features a session-isolated recent files list, a floating window mode, and full Markdown rendering (including code blocks and tables), automatically adapting to dark/light theme changes. To install, ensure the DSH profile is set to `web`, add the plugin via the `dsh plugin add` command from the GitHub repository `poiuyjie/dsh-md-preview`, and ensure the Node.js version is 20.3 or higher.