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
2224ccdea2Julius Marminge committed on 9/1/2026, 4:32:06 AMparent048bda5
4 files changedLine totals unavailable