RCLUSTER-WP-0019: tolerate unsimulatable backup copy in --check

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Assistant: claude-code
Assistant-Model: opus
Assistant-Process: 605711@bnt-lap001
Assistant-Session: 1f5e2256-181f-49ed-b7b1-a1c34bf37a61

ansible/k3s-kubeconfig-mode.yml

@@ -169,6 +169,8 @@
           when: unit_is_preimage
 
         - name: Back up original unit (root-only)
+          # In --check the backup directory is not created, so the copy cannot be simulated.
+          ignore_errors: "{{ ansible_check_mode }}"
           ansible.builtin.copy:
             src: "{{ k3s_unit_path }}"
             remote_src: true