Fix PowerShell deploy stdin encoding

backend/tests/test_sprint31_unraid_template.py

@@ -133,6 +133,8 @@ def test_tower_deploy_build_uses_remote_env_ai_setting_by_default() -> None:
 def test_powershell_tower_deploy_streams_remote_script_to_bash() -> None:
     powershell = (ROOT / "scripts" / "deploy_tower.ps1").read_text(encoding="utf-8")
 
+    assert "[System.Text.UTF8Encoding]::new($false)" in powershell
+    assert "$OutputEncoding = $utf8NoBom" in powershell
     assert "bash -s" in powershell
     assert "$remoteScript | ssh" in powershell
     assert "REMOTE_PATH='$RemotePath'" in powershell