fix(chat): prevent stale timeline scroll and rerenders

- Disable LegendList end-maintenance that could snap after user scrolling
- Cancel stale imperative scrolls and release settled turn anchors
- Stabilize handoff run data to avoid per-event timeline rerenders
6609f3a86bJulius Marminge committed on 9/5/2026, 4:54:23 AMparenta80533b
4 files changedLine totals unavailable