dsh-plugin-descriptions: Adding Feature Descriptions to the DSH Web Plugin Settings Section

The DeepSeek Harness plugin `dsh-plugin-descriptions` addresses the issue for developers that the official plugin list only displays metadata without functional descriptions. The plugin adds a new “Plugin Descriptions” tab before the official list, displaying plugin details grouped by functional domain. It supports automatically reading descriptions from `package.json` and includes built-in Chinese descriptions for commonly used plugins. With search and filtering capabilities, it helps developers quickly identify the purpose and status of installed plugins.