dsh-plugin-precheck: DeepSeek Harness Plugin Installation Pre-check Assistant

`dsh-plugin-precheck` is a DeepSeek Harness plugin designed to resolve dependency conflicts and startup failures during third-party plugin installation. It adds an “Install Precheck” tab to the Web GUI to perform version resolution, compatibility comparison, configuration tree conflict detection, and isolated trial installation and startup. In addition, the plugin intercepts market plugin installation and update requests at the browser layer, ensuring that only fully validated operations take effect. By using an isolated environment and logical interception, the tool provides developers with a secure plugin installation environment.