Resolve the multiplicative factor for a unit_time conversion

Shared between set_unit_time.aniframe() and set_unit_time.anievent(). Validates to_unit, reads the current unit_time from metadata, and returns the calibration factor to apply to the temporal columns. Emits an informational message and returns 1 (no-op on data values) when the source unit is "frame" / "unknown" and no calibration factor was supplied.

Usage

resolve_unit_time_calibration(data, to_unit, calibration_factor)