Install OpenSSH Server from the Win32-OpenSSH zip

Carry the zip for the host architecture in the seed ISO and add
06-Install-OpenSSH-Zip-Admin.bat, which installs from it instead of
Windows Update. Update vm-images.

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

README.md

@@ -174,9 +174,12 @@ VirtIO ISO with `pnputil` on arm64), without which the guest has no network on
 arm64. The installer includes the VirtIO drivers, SPICE vdagent, and QEMU Guest
 Agent. The launcher exposes the vdagent channel for host/guest clipboard
 integration and the QEMU Guest Agent at `.vm/windows11/qemu-guest-agent.sock`.
-Change the password after first login. The OpenSSH Server is downloaded through
-Windows Update, which can be slow, so it is not installed automatically: run
-`05-Install-OpenSSH-Admin.bat` from the `Installers` folder on the desktop as
+Change the password after first login. The OpenSSH Server is not installed
+automatically. Run `05-Install-OpenSSH-Admin.bat` from the `Installers` folder on
+the desktop to install it through Windows Update, which can be slow, or
+`06-Install-OpenSSH-Zip-Admin.bat` to install it from the Win32-OpenSSH zip for
+the host architecture, which the seed ISO carries (downloaded by
+`vm-images/download-images.sh openssh-win`), as
 administrator, then connect with `ssh guofang@localhost -p 2222`; it also installs
 the host's configured SSH public key for passwordless administrator login.
 The Windows VM hardware (8G memory, 8 CPUs, system disk, devices)