Pull-down-at-top called reloadThread (reload newest 500 + scroll to bottom), so
reaching the oldest message yanked the view to the newest — jarring, especially on a
single page. Now the pull gesture calls loadOlder: it pages in older history keeping
scroll position, or no-ops when there's nothing older. Never jumps to the bottom.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>