dsh-session-topics: DeepSeek Harness Sidebar Session Topic Grouping Plugin

`dsh-session-topics` is a pure client-side plugin designed to address the limitation of the DeepSeek Harness sidebar, which only supports grouping by workspace. It introduces a “topic” axis, expanding the sidebar structure into “workspace → topic → subtopic → session,” and supports drag-and-drop sorting, archiving, a context menu, and local data persistence. The plugin has zero dependencies, incurs no cost, is implemented by taking over official slots, can be installed from GitHub, and includes a data backup and recovery mechanism.