feat(qemu-ci): scope internal breakpoints as steps:NAME or steps-guix:NAME with default steps-guix recopy

steps-guix/jump/break.sh

@@ -0,0 +1,23 @@
+#!/bin/sh
+#
+# SPDX-License-Identifier: GPL-3.0-or-later
+
+set -e
+
+# Optional in some preseed/testing contexts.
+if [ -f /steps/bootstrap.cfg ]; then
+    # shellcheck disable=SC1091
+    . /steps/bootstrap.cfg
+fi
+
+# For VM/metal runs, stop immediately so the current disk state can be reused.
+if [ "${CHROOT}" = False ]; then
+    swapoff -a >/dev/null 2>&1 || true
+    sync
+    echo u > /proc/sysrq-trigger || true
+    mount -o remount,ro / || true
+    echo o > /proc/sysrq-trigger || poweroff -f || true
+    while true; do sleep 1; done
+fi
+
+exit 0