dsh-message-preview: Right-side Message Navigation Bar for DeepSeek Harness Web UI

dsh-message-preview is a DSH Web UI plugin maintained by asukasec, designed to address the inconvenience of manually scrolling through long sessions to find specific messages. The plugin adds a message navigation bar on the right side of the session, indexing only user-sent messages while excluding tool notifications and background tasks. Key features include: automatic highlighting of the current reading position; hover functionality to display message sequence number, relative time, and text preview; smooth scrolling and historical message loading upon clicking navigation blocks to jump to specific positions; and support for keyboard navigation (Tab to focus, arrow keys to select, Enter to jump). The navigation blocks adapt their layout automatically, hide when fewer than two user messages are present, and default to displaying only a position indicator, expanding when the mouse approaches the right edge. Interface text automatically switches based on DSH language settings. Installation requires DeepSeek Harness 0.1.0-rc.6.