feat: compare accountability update deltas

workplans/RAIL-FAB-WP-0018-accountability-root-discovery-update-loop.md

@@ -231,7 +231,7 @@ Result:
 
 ```task
 id: RAIL-FAB-WP-0018-T05
-status: todo
+status: done
 priority: medium
 state_hub_task_id: "c2f28b34-de32-4090-8782-5d00541b9018"
 ```
@@ -257,6 +257,25 @@ Done when:
   changes are highlighted;
 - unchanged sources are not needlessly promoted.
 
+Result:
+
+- Added `schemas/accountability-update-delta.schema.yaml` for
+  `AccountabilityUpdateDelta` payloads.
+- Added `build_update_delta()` to compare current and previous identity
+  projections plus ownership reviews.
+- Deltas distinguish candidate graph node additions/changes/removals,
+  candidate graph edge additions/changes/removals, ownership changes,
+  containment changes, review-state changes, blocker changes, and unchanged
+  nodes/edges.
+- Added `railiance-fabric discover-roots --delta` with optional
+  `--previous-identity-projection` and `--previous-ownership-review` inputs.
+- Added tests proving unchanged runs do not require promotion and ownership
+  review changes are highlighted.
+- Documented update deltas in the manifest and operator docs.
+- Verified with `python3 -m pytest tests/test_accountability_root_adapters.py -q`,
+  `python3 -m railiance_fabric.cli discover-roots --max-items-per-root 5 --delta`,
+  and full `python3 -m pytest`.
+
 ## T06 - Bootstrap The Current Railiance Rebuild
 
 ```task