refactor(winrm.py): fix pipeline handling, NTLM mapping, deduplicate auth logic

- Fix cmd.split() breaking pipelines and named parameters: params=None
  now uses add_script() for arbitrary PowerShell, params given uses
  add_cmdlet() for JEA-optimal execution
- Fix NTLM transport incorrectly mapped to 'negotiate' (now maps to 'ntlm')
- Add dict params support via add_parameter(name, value)
- Extract _build_auth() and _map_transport() helpers to remove duplication
- Add _quote_ps_value() for safe PowerShell quoting in pywinrm fallback
- Update docstrings to reflect new params behavior

Author: markuslf