identify.axis_frequency
Measure a configured bounded axis in both directions with fresh wavelength and optical-quality samples. Holds competing loops; stores a signed slope proposal, raw samples, hysteresis and residuals, ROOT vector plot and LuaLaTeX PDF. It does not adopt calibration. Suspected mode discontinuities invalidate the fit. Cancellation holds the last point; no speculative restoration.
Offline implementation only. Hardware operation requires commissioning and reviewed laser configuration. No production changes are included.