Dsh Timeline Rail

Key features

• Evenly spaced ticks — one short horizontal line per user message along a 1px track, with a fixed 12px gap
• long histories scroll inside the rail instead of compressing the marks.
• Centered marks — each horizontal tick is centered on the vertical rail, keeping the timeline axis visually balanced.
• Complete-history loading — after the session opens, the rail automatically loads earlier history pages in series until no pages remain, and adds ticks as each page arrives.
• Hover to preview — a compact wide card shows the user message (#N) in bold, clamped to 2 lines, followed by the assistant reply clamped to 3 lines