Viewing a thread in mobile app starts the scroll controller at the first message, not the most recent

[colbymaloy]

Motivation
The user has to scroll an enormous amount to get to the most recent message

[dioptx]

This appears to be fixed by #4702 (merged 2026-08-12) — thread opens now wait for authoritative hydration before settling on the latest reply. Reproduced the symptom on the current App Store build; the fix is on main but not yet in a shipped mobile release.