Timeline
componentA two-column timeline whose rail is drawn in as the list scrolls past, with a big sticky label holding each entry's date beside it while you read.
- Scroll the list — the rail draws in behind you and stops exactly as the last entry is reached.
- Each label sticks in its own column and gives way to the next one, so the year you are reading under is always the one on screen. Below `md` the two columns collapse and the label moves inline above the card.
- Turn the fill off and the rail is a plain line; nothing else changes.
