dsh-qnav: Right-Side Navigation Bar for Long Conversations

The dsh-qnav plugin adds a navigation bar to the right edge of DeepSeek Harness (DSH) to address the difficulty of locating issues in long conversation flows. It accurately extracts genuine user questions and supports click-to-reference jumping, automatic filtering of non-user lines, dark mode compatibility, and current-location highlighting. It uses MutationObserver to monitor content changes and includes HMR safety mechanisms. It is easy to install and can be used stably across multiple platforms without modifying native code, though it is limited by visibility scope and ultra-long conversation density.