add minimal reproducer for qtbase wayland screen use-after-free

test/screen-uaf-reproducer/trigger.sh

@@ -0,0 +1,44 @@
+#!/usr/bin/env bash
+# Trigger rapid output power-cycling to provoke the Qt Wayland screen UAF.
+# Run the reproducer binary first, then this script in another terminal.
+#
+# Usage: ./trigger.sh [iterations]
+#   iterations: number of off/on cycles (default 20)
+
+set -euo pipefail
+
+cycles="${1:-20}"
+
+if command -v niri &>/dev/null && niri msg version &>/dev/null; then
+    echo "Detected Niri - using niri msg"
+    for i in $(seq 1 "$cycles"); do
+        echo "cycle $i/$cycles"
+        niri msg action power-off-monitors
+        sleep 0.3
+        niri msg action power-on-monitors
+        sleep 0.5
+    done
+elif command -v wlr-randr &>/dev/null; then
+    output=$(wlr-randr --json 2>/dev/null | python3 -c \
+        "import sys,json; print(next(o['name'] for o in json.load(sys.stdin) if o['enabled']))" 2>/dev/null \
+        || wlr-randr | grep -oP '^\S+' | head -1)
+    if [ -z "$output" ]; then
+        echo "error: could not detect an output via wlr-randr" >&2
+        exit 1
+    fi
+    echo "Detected wlroots compositor - toggling output $output"
+    for i in $(seq 1 "$cycles"); do
+        echo "cycle $i/$cycles"
+        wlr-randr --output "$output" --off
+        sleep 0.3
+        wlr-randr --output "$output" --on
+        sleep 0.5
+    done
+else
+    echo "error: neither niri nor wlr-randr found" >&2
+    echo "Manually unplug/replug a monitor while the reproducer is running." >&2
+    exit 1
+fi
+
+echo "Done. If the reproducer is still alive, the bug did not trigger."
+echo "Try increasing iterations or adding more surfaces."