dsh-question-rail: DeepSeek Harness Chat Navigation Plugin

`dsh-question-rail` is an open-source plugin designed specifically for the web version of DeepSeek Harness (DSH) to address the pain points of locating questions and tracing back context in long conversations. The plugin generates a question rail along the right edge of the conversation interface, supporting hover-to-expand, smooth scrolling on click to jump to a question, and highlight flashing for precise positioning. It offers features such as automatically loading the complete history, dark mode support, keyboard navigation, and visibility only in the conversation view. Users can install it using the specified command, and it will be ready to use after restarting and refreshing.