dsh-instance-manager: DeepSeek Harness Sidebar Instance Manager

`dsh-instance-manager` is a local plugin for DeepSeek Harness that centrally manages instances on ports 3080–3129 through a sidebar. It supports viewing instance details, starting new instances, gracefully stopping instances, and viewing logs and sessions, while also providing remote instance inspection and Agent tool functionality. The project supports environment variables and configuration settings, and includes built-in security mechanisms—such as access control, token validation, and a local guard—to ensure operations are restricted to the local machine.