dsh-startup-command: DeepSeek Harness Web Plugin

`dsh-startup-command` is a DeepSeek Harness Web plugin developed by Kagurazakayashi that automatically executes custom commands after the web service starts. It supports placeholders (such as {url} and {home}) and sequential execution of command arrays, and runs independently using a non-blocking design. Users can install it via npm and mount it in a configuration file, then configure browser or helper program startup actions in the settings interface or YAML. Be careful to avoid conflicts with DSH's built-in browser functionality and ensure the required Node.js version is met.