macOS Scaleway job metrics and steps share one timeline

Step timestamps on macOS Scaleway runner job charts now line up with the metric samples beneath them. A Scaleway golden-base VM can be handed a job seconds after boot, before macOS timed has synced a clock that started minutes behind, so the GitHub runner and the metrics sampler both stamped their data off a clock that drifted into alignment only mid-run. The runner-image now forces a synchronous NTP step right after the dispatch call succeeds and before the runner/sampler start, so steps and metrics share one timeline from the first sample.