Append-or-update metadata/measurement_method.csv by (dataset_key, measurement_type)
Source: R/registry_measurement_face.R
register_measurement_method.RdOne row per series in measurements.json (D4): platform in bottle | ctd | underway | lab | net | mast; nerc_l22 only on an exact device match (empty
otherwise, per the metadata-registries skill's exact-match rule); steps
and bibkeys are " | "-joined lists on one CSV cell. A method the source
cannot support ships with principle empty and source = "not found" —
never a guess.