The scroll-position memory introduced in 0.17.2 still produced a visible
"chat appears at the top then jumps" frame when switching back into a
conversation. Cause: both scroll-affecting effects (auto-bottom on new
messages, restore on chat re-entry) used useEffect, which fires AFTER
the browser paints the freshly-committed DOM. So users saw scrollTop=0
for one frame before the effect ran and corrected it.
Switching both to useLayoutEffect moves the scroll write into the same
commit phase as the message-list DOM update, so the very first paint
already shows the correct position — single paint, no flicker.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
