fix(tests): provide a window manager for Linux Electron CI (#19007)

.github/scripts/e2e-with-window-manager.sh

@@ -0,0 +1,26 @@
+#!/usr/bin/env bash
+set -euo pipefail
+openbox --sm-disable > /tmp/orca-e2e-window-manager.log 2>&1 &
+wm_pid=$!
+cleanup() {
+  kill "$wm_pid" 2>/dev/null || true
+  wait "$wm_pid" 2>/dev/null || true
+}
+trap cleanup EXIT
+ready=false
+for attempt in {1..100}; do
+  if xprop -root _NET_SUPPORTING_WM_CHECK 2>/dev/null | rg -q 'window id # 0x[1-9a-fA-F]'; then
+    ready=true
+    break
+  fi
+  if ! kill -0 "$wm_pid" 2>/dev/null; then
+    cat /tmp/orca-e2e-window-manager.log
+    exit 1
+  fi
+  sleep 0.1
+done
+if [ "$ready" != true ]; then
+  echo 'Window manager did not acquire the Xvfb root window' >&2
+  exit 1
+fi
+"$@"