Add GPU and NTP API facade helpers

[spyroot]

Summary

• Add typed facade dataclasses and helpers for gpu-metrics output.
• Add a guarded NTP helper that previews by default and delegates application to ntp-set.
• Extend facade coverage with command-payload tests and GB300 corpus-backed command registry checks.

Tests

• conda run -n idrac_ctl pytest -q tests/test_api_facade.py (7 passed)
• conda run -n idrac_ctl ruff check redfish_ctl/api.py tests/test_api_facade.py (All checks passed)
• conda run -n idrac_ctl pytest -q (793 passed, 57 skipped)