fix(chat): align scrollbar/keyboard detach with wheel/touch re-engage threshold

The onScroll detach branch set only stickyRef.current = false, leaving
userDetachedRef false, so a scrollbar-drag or keyboard detach kept the lenient
30px (STICK_THRESHOLD) re-engage threshold instead of the strict 5px
(REATTACH_THRESHOLD) used after wheel/touch. A programmatic virtualizer re-pin
landing within 30px could then snap autoscroll back on right after the user
deliberately scrolled away. Reuse the detach() helper so all detach paths set
userDetachedRef consistently.

Author: waleedlatif1

apps/sim/hooks/use-auto-scroll.ts

@@ -147,7 +147,7 @@ export function useAutoScroll(
         scrollTop < prevScrollTopRef.current &&
         scrollHeight <= prevScrollHeightRef.current
       ) {
-        stickyRef.current = false
+        detach()
       }
 
       prevScrollTopRef.current = scrollTop