@dsh-external/dsh-chat-jumper: DSH Chat Dot Navigation

`@dsh-external/dsh-chat-jumper` is a DSH plugin maintained by Cloud-J, intended to solve the problems of difficult page scrolling and slow position-finding in long conversations. It provides a vertical column of dots on the right side of the page, where each dot corresponds to one user question. The plugin supports hover previews, smooth scrolling, current-position highlighting, and automatic loading of historical messages. Users can quickly navigate by clicking a dot. Its data is based on conversation snapshots and does not rely on DOM scanning, ensuring that even unrendered historical messages are accurately counted.