Install OpenSSH Server during Windows setup

Install it at first logon from the Win32-OpenSSH zip on the seed ISO via
Configure-Windows.ps1 -InstallOpenSSH, replacing the manual 05/06 batch
files. The administrator public key now comes from the host
(SSH_PUBLIC_KEY_FILE or ~/.ssh/id_*.pub) instead of being hardcoded.

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

run-windows11.py

@@ -304,6 +304,13 @@ if installing_from_iso:
     seed_sources = [seed_dir / "Autounattend.xml", seed_dir / "Configure-Windows.ps1",
                     *sorted(seed_dir.glob("[0-9][0-9]-*.bat"))]
 
+    # build-seed.sh embeds the administrator SSH public key.
+    ssh_key = os.environ.get("SSH_PUBLIC_KEY_FILE") or next(
+        (str(k) for n in ("id_ed25519", "id_ecdsa", "id_rsa")
+         if (k := Path.home() / ".ssh" / f"{n}.pub").is_file()), None)
+    if ssh_key:
+        seed_sources.append(Path(ssh_key))
+
     # The seed carries the OpenSSH zip for this architecture; build-seed.sh
     # downloads it when missing.
     seed_sources.append(Path(capture(