CBOR: carry ice_ring_score in the END block

The per-image ice ring score was encoded for every DataMessage but never
for the END message, although docs/CBOR.md has always listed it there and
both NXmx::EndResultVectors and HDF5MetadataSource expect it. Any dataset
written over the stream therefore had no /entry/MX/iceRingScore, and under
NXmxIntegrated - where the whole-run vector is the only copy - the score
was lost entirely.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

frame_serialize/CBORStream2Deserializer.cpp

@@ -1425,6 +1425,8 @@ namespace {
                 GetCBORUInt8Array(value, message.image_indexed);
             else if (key == "v_bkg_estimate")
                 GetCBORFloatArray(value, message.v_bkg_estimate);
+            else if (key == "ice_ring_score")
+                GetCBORFloatArray(value, message.ice_ring_score);
             else if (key == "profile_radius")
                 GetCBORFloatArray(value, message.profile_radius);
             else if (key == "mosaicity")