feat: close preprod observability loop

docs/FEATURES/observability.md

@@ -78,3 +78,17 @@ Initial alerts should cover:
 - email delivery failures
 - blob storage failures
 - background job failures
+
+## Workflow Health Gauges
+
+Database-derived workflow health metrics should be sampled periodically instead of emitted per request.
+
+Initial gauges should cover:
+
+- content item counts by status
+- feedback report counts by status
+- pending workspace invites
+- content stale in approval
+- active workspace counts over 24-hour and 7-day windows
+
+These are operator health signals. They should stay aggregate enough to avoid high-cardinality metric labels.