refactor(steps-guix): align linux64 handover with upstream jump flow and end with shared after

steps-guix/improve/after.sh

@@ -0,0 +1,4 @@
+#!/bin/sh
+# SPDX-License-Identifier: GPL-3.0-or-later
+
+exec /steps/improve/after.sh

steps-guix/improve/linux64.sh

@@ -1,32 +0,0 @@
-#!/bin/bash
-#
-# SPDX-FileCopyrightText: 2026 Luo Yanpan
-#
-# SPDX-License-Identifier: GPL-3.0-or-later
-
-set -e
-
-new_kernel="/boot/vmlinuz-linux64"
-current_kernel="/boot/vmlinuz"
-backup_kernel="/boot/vmlinuz-32bit.backup"
-
-if [ ! -f "${new_kernel}" ]; then
-    echo "Missing new kernel image: ${new_kernel}" >&2
-    exit 1
-fi
-
-if [ -f "${current_kernel}" ]; then
-    cp -af "${current_kernel}" "${backup_kernel}"
-fi
-cp -af "${new_kernel}" "${current_kernel}"
-sync
-
-mkdir -p /etc
-if [ "${BARE_METAL}" = True ]; then
-    kexec -l "${current_kernel}" \
-        --append="root=/dev/sda1 init=/init rw rootwait"
-else
-    kexec -l "${current_kernel}" --console-serial \
-        --append="console=ttyS0 root=/dev/sda1 init=/init rw rootwait"
-fi
-kexec -e