Card: metadata v2 as the default Dataset Viewer table; catalog kept as a second config

Viewer configs only; no data file changed. Gated card also notes the 69 samples on main added 2026-10-30 that metadata v2 does not cover yet.

README.md

@@ -8,6 +8,9 @@ tags:
 - spatial-transcriptomics
 - metadata
 configs:
+- config_name: metadata_v2
+  data_files: metadata/v2/samples_metadata_v2.parquet
+  default: true
 - config_name: samples
   data_files: catalog/samples.parquet
 ---
@@ -253,6 +256,9 @@ a selection).
 `metadata/v2/` adds a curated table on top of the same 12,163 samples. No data file changed: the paper release is
 still tag `v1.0.0-20261025`; the current metadata is tag `metadata-v2.2.1-20261106`.
 
+In the Dataset Viewer, `metadata_v2` (the default) shows this table and `samples` shows the catalog
+(`catalog/samples.parquet`).
+
 - `samples_metadata_v2.parquet` / `.csv` has one row per sample:
   - organ (43 sites);
   - UBERON tissue term (11,605 samples);