dsh-reveal-files: Add a File Operations Menu to DeepSeek Harness Artifact Rows

`dsh-reveal-files` is a plugin for DeepSeek Harness Web (`dsh web`) designed to optimize interactions with generated files. By default, clicking a file chip no longer opens the file directly; instead, it triggers a compact menu that supports actions such as opening the file, copying the path, showing it in the file browser, and opening the directory in a terminal. The plugin has minimal environment requirements, relying only on Node.js, supports multiple platforms, and runs entirely locally, making it a practical tool for improving file operation efficiency in agent development.