omdsh-plughub: DeepSeek Harness Plugin Hub

`omdsh-plughub` is the plugin center plugin for DeepSeek Harness (DSH), offering centralized management of plugin installation, updates, enabling/disabling, and configuration through a GUI. Located under the "Settings" tab, it aggregates plugin information from local sources, registries, and GitHub. It provides an intuitive list interface, supports one-click installation of new plugins, and allows configuration via auto-generated forms. Updates and removals are similarly straightforward, and disabling a plugin only removes its dependencies from the layer stack without affecting `node_modules` files. This tool significantly reduces plugin maintenance costs and is essential for plugin management in the DSH ecosystem.