QMP Reference manual and code results (json) do not match for query-migrate

Host environment

• Operating system: SUSE Linux Enterprise Server (SLES) 15 SP7
• OS/kernel version: Linux v 6.4.0-150700.53.16-default #1 SMP PREEMPT_DYNAMIC Wed Sep 10 13:03:54 UTC 2025 (942e5de) x86_64 x86_64 x86_64 GNU/Linux
• Architecture: x86
• QEMU flavor: qemu-system-x86_64
• QEMU version: QEMU emulator version 9.2.4 (SUSE Linux Enterprise 15)
• QEMU command line: (libvirt) - Does not apply

Emulated/Virtualized environment

• Operating system: SLES 15 SP7
• OS/kernel version: same
• Architecture: x86 (KVM used, no TCG)

Description of problem

the QMP "query-migrate" command returns correct data in most cases, but for "completed" migration status it does not return the transfer statistics.

The QMP example in the QMP Reference Manual shows:

 { "execute": "query-migrate" }
 { "return": {
         "status": "completed",
         "total-time":12345,
         "setup-time":12345,
         "downtime":12345,
         "ram":{
           "transferred":123,
           "remaining":123,
           "total":246,
           "duplicate":123,
           "normal":123,
           "normal-bytes":123456,
           "dirty-sync-count":15
         }
      }
  }

https://qemu-project.gitlab.io/qemu/interop/qemu-qmp-ref.html

But this is not what QEMU returns for completed migrations:

The JSON string I get is:

$ virsh qemu-monitor-command --domain a239fbf6-d219-4b1b-b24b-ff3e1738b891 --cmd '{ "execute": "query-migrate" }'
{"return":{"status":"completed"},"id":"libvirt-556"}

Steps to reproduce

1. Do a simple live migration with shared storage (virsh migrate ...)
2. Issue virsh qemu-monitor-command --cmd '{ "execute": "query-migrate" }' immediately afterwards
3. See that the returned data is correct during the transfer.
4. wait until migration is completed
5. Issue virsh qemu-monitor-command --cmd '{ "execute": "query-migrate" }'
6. Witness the lack of any statistics, which contrasts with the documentation.

Suggested fix

Return the statistics also in the completed case, which matches documentation and is useful in practice.