The per-image ice_ring_score was written to the data files (HDF5DataFilePluginMX)
but the master-file write and the stored-file read path were missing, so opening a
processed HDF5 (e.g. in jfjoch_viewer) would not surface it. Mirror bkg_estimate:
write /entry/MX/iceRingScore in the NXmx master (HDF5NXmx, from EndMessage), and
read it back in HDF5MetadataSource into the dataset (master + data-file reads) and
per image into the message. Verified the write; the read is a byte-for-byte mirror
of the working bkgEstimate round-trip.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>