Windows launcher only creates a differential disk; seed via Unattend.xml

run-windows11.py no longer installs Windows or touches ISO/img files: it
creates a QCOW2 overlay on the base image (made by vm-images/build-windows-base.sh)
and, when the disk is created, mounts seed.iso. Windows reads the Unattend.xml
in its root during the specialize and OOBE passes (host name, account, auto
logon, Remote Desktop) and Configure-Windows.ps1 then installs OpenSSH with the
host's key, turns off Windows Update and copies the installer scripts.

The VM hardware uses devices with inbox Windows drivers (IDE/NVMe, e1000e,
ramfb on arm64), since the base image has no VirtIO drivers. Autounattend.xml
moves to vm-images; the vm-images pointer is updated.

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

qemu/windows11/linux-amd64.ini

@@ -11,8 +11,7 @@
   type = "q35"
 
 # The system disk is attached through IDE so that Windows can boot before the
-# VirtIO storage driver is installed; the installation media of
-# --install-from-iso use ide.1 to ide.3.
+# VirtIO storage driver is installed.
 [device "system_disk-dev"]
   driver = "ide-hd"
   drive = "system_disk"