deepseeh-harness-ultra-slash: A separate group of plugin commands in the DSH / menu

# Introduction People using DeepSeek Harness (hereinafter referred to as DSH) largely rely on the `/` menu in the chat input box. DSH's philosophy is "Everything is a plugin." When many plugins are installed, finding commands becomes a practical issue. Another high-frequency need occurs mid-conversation: you think of a new instruction you want the model to process in the next step but do not want to interrupt the ongoing dialogue. The loadingvx Ultra Slash plugin handles both of these simultaneously: it separates plugin commands into a separate group in the `/` menu, distinct from DSH's built-in commands, and provides four commands: `/steer`, `/new`, `/skill`, and `/docs`, as well as the ability to assign short names to frequently used `/steer` content. The following introduces its features, installation, and...