ranking_version v3->v4: activate saturation (active_core_ids consumer shipped)

Saturated datasets (J-SPAW_LA) are now excluded from the Mean/coverage/tier
denominator board-wide and rendered as frozen tombstone columns. Display-only
bump; the freeze is already live from the arena code deploy.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

CHANGELOG.yaml

@@ -41,3 +41,4 @@ events:
   - {date: 2026-06-10, type: note, text: "Re-ingest to subscribe XMAD for webhook routing"}
   - {date: 2026-06-20, type: note, text: "manifest schema_version 1->2 (rides package 0.4.0): dataset_entry gains status/saturated_at/metric/category/penalty/verification + top-level contamination_overrides; submission schema 4->5 (enum, back-compat). ranking_version stays v3 (no scoring-rule change yet)"}
   - {date: 2026-06-20, type: note, text: "J-SPAW_LA declared saturated (status: saturated, saturated_at: 2026-06-20); field is inert until the arena active_core_ids consumer ships (stage 5)", dataset_id: "SpeechAntiSpoofingBenchmarks/J-SPAW_LA"}
+  - {date: 2026-06-21, type: note, text: "ranking_version v3->v4: active_core_ids consumer shipped (stage 5). Saturated datasets are now excluded from the Mean/coverage/tier denominator board-wide and rendered as greyed 'frozen' tombstone columns (rightmost, out of the Mean). J-SPAW_LA is the first frozen dataset; it stays fully browseable on the Per-dataset tab."}

manifest.yaml

@@ -1,4 +1,4 @@
-ranking_version: v3
+ranking_version: v4
 schema_version: 2
 
 metrics_in_use: