disk-deactivate: wipe raid arrays before stopping them

Previously, the `disk-deactivate` script stopped mdadm arrays before
wiping the underlying physical disks. This caused filesystems with
backup superblocks (like BTRFS at 64 MiB and 256 GiB offsets) to
survive the wipe, as the backups were striped across the physical
disks and missed by `wipefs` on the raw block devices.

When the array was reassembled during reprovisioning, the filesystem
superblocks realigned. `disko` would detect the old filesystem via
`blkid` and silently skip the `mkfs` step, leaving stale data intact.

This commit adds a `wipefs --all` command against the assembled RAID
device *before* stopping it, ensuring all filesystem signatures and
backup superblocks are cleanly destroyed.

disk-deactivate/disk-deactivate.jq

@@ -60,6 +60,7 @@ def deactivate:
     ]
   elif (.type | contains("raid")) then
     [
+      "wipefs --all -f \(.path | shellquote)",
       "mdadm --stop \(.name | shellquote)"
     ]
   else