dsh-scroll-timeline: User Message Scroll Timeline for DSH Chat Sidebar

`dsh-scroll-timeline` is a browser-side third-party plugin for the DSH web chat interface, designed to address the need for quickly locating user messages in long conversations. It generates a vertical rail of nodes along the right edge of the sidebar, where each user message corresponds to a horizontal node, supporting hover-to-preview message content and click-to-scroll smooth navigation. The plugin is licensed under MIT, derived from `vlln/dsh-navbar`, driven by official anchor attributes without requiring additional commands or routes, and has an empty mount on the Node side. Core features include a peak bar that follows the reading position, nodes expanding at specific ratios on hover to create a magnetic effect, and automatic hiding when there are few messages or on non-chat pages. Users can install it with a single git command and enable it in the settings panel. The plugin supports width adjustment via CSS variables and is compatible with `prefers-re