Use imagescroll feature.

regress/image-scroll-no-erase.sh

@@ -0,0 +1,16 @@
+#!/bin/sh
+
+# The PR's trusted-scroll erase regression: inspect terminal erases directly
+# rather than depending on a particular debug log message.
+
+PATH=/bin:/usr/bin
+TERM=screen
+export TERM
+[ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
+
+python3 -B - "$TEST_TMUX" <<'PY'
+import sys
+from image_scroll import check_scroll
+
+check_scroll(sys.argv[1], True, no_erase=True)
+PY