Fix iOS scroll test: poll for click event instead of fixed 15s sleep

The fixed 15s sleep after detecting setRoot wasn't always long enough for
'Click dispatched' to appear in the persistent log store. Replace with an
active poll (up to 30s) for 'Click dispatched' in the stream log, followed
by a 5s buffer before retrieving the persistent log. This matches how the
buttons test already polls for its terminal event.

Tokens: ~5k

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: jappeace-sloth

test/ios/scroll.sh

@@ -37,13 +37,15 @@ if [ $render_done -eq 0 ]; then
     wait_for_log "$STREAM_LOG" "setRoot" 60 || true
 fi
 
-# Auto-tap fires 3s after render; wait for log flush
-sleep 15
+# Auto-tap fires 3s after render; poll stream log until click appears or 30s timeout
+wait_for_log "$STREAM_LOG" "Click dispatched" 30 || true
+# Extra buffer so the persistent log store catches up before log show
+sleep 5
 
 kill "$LOG_STREAM_PID" 2>/dev/null || true
 sleep 1
 
-# Retrieve full log; fall back to stream log if empty
+# Retrieve full log from persistent store; fall back to stream log if empty
 FULL_LOG="$WORK_DIR/scroll_full.txt"
 get_full_log "$SCROLL_START" "$FULL_LOG"