feat: add support for per-cluster centroid datasets in sequence processing

Author: AStaroverov

.changeset/per-cluster-centroid-dataset.md

@@ -0,0 +1,6 @@
+---
+"@platforma-open/milaboratories.sequence-properties.workflow": patch
+"@platforma-open/milaboratories.sequence-properties.model": patch
+---
+
+Add support for per-cluster centroid datasets (clonotype-clustering). The model accepts a 2-axis `[sampleId, centroidId]` anchor, and the workflow treats the synthetic per-cluster centroid sequence as legacy-bulk VDJ for sequence pulling.