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>

seediso/windows11/build-seed.sh

@@ -32,10 +32,10 @@ fi
 work_dir="$(mktemp -d)"
 trap 'rm -rf "$work_dir"' EXIT
 sed "s/processorArchitecture=\"amd64\"/processorArchitecture=\"${answer_arch}\"/" \
-  "$script_dir/Autounattend.xml" >"$work_dir/Autounattend.xml"
+  "$script_dir/Unattend.xml" >"$work_dir/Unattend.xml"
 
 seed_files=(
-  "$work_dir/Autounattend.xml"
+  "$work_dir/Unattend.xml"
   "$script_dir/Configure-Windows.ps1"
   "$openssh_zip"
 )