dsh-right-drawer: DeepSeek Harness Right Drawer Host

The DeepSeek Harness plugin `dsh-right-drawer` provides a host solution for the right-side panel on the Web. It manages content plugins through the `dockPanels` registry, supports full-height drawer display, and features automatic tab stacking, drag-to-adjust width (280–900px), and coordinated layout with the scheme panel. Adopting a plugin-based architecture, content plugins can be integrated simply by registration, making it suitable for developers who need to build complex sidebar layouts.