Deleting a draft after confirming the order also deletes the confirmed order

Steps to reproduce:

1. New Quote → fill some fields → Save as Draft
2. Reopen the draft → finish all steps → submit → order is confirmed
3. Both the draft and the confirmed order now exist
4. Delete the draft (cleaning up duplicates)
5. The confirmed order is also gone — have to re-enter from scratch

Confirming a draft should remove the draft so there's nothing to accidentally delete.