add Fabric read model rollback activation

Assistant: codex
Assistant-Model: gpt-5.6-sol
Assistant-Session: 01a053ff-1d6f-7fe2-ac1c-a6eb40a42a0c

tests/test_routers_core.py

@@ -1545,6 +1545,33 @@ class TestFabricGraphReadModel:
         assert latest_flags[first_id] is False
         assert latest_flags[second_id] is True
 
+    async def test_retained_valid_import_can_be_activated_for_rollback(self, client):
+        r = await client.post("/fabric/graph-exports", json=_fabric_graph_export())
+        first_id = r.json()["import_run"]["id"]
+        r = await client.post("/fabric/graph-exports", json=_fabric_graph_export(extra_node=True))
+        second_id = r.json()["import_run"]["id"]
+
+        r = await client.post(
+            f"/fabric/graph-exports/{first_id}/activate",
+            json={"requested_by": "cutover-test"},
+        )
+        assert r.status_code == 200, r.text
+        assert r.json()["activated"] is True
+        assert r.json()["idempotent"] is False
+        assert r.json()["previous_import_id"] == second_id
+        assert r.json()["import_run"]["id"] == first_id
+        assert (await client.get("/fabric/graph/summary")).json()["node_count"] == 3
+
+        r = await client.post(f"/fabric/graph-exports/{first_id}/activate")
+        assert r.status_code == 200, r.text
+        assert r.json()["activated"] is False
+        assert r.json()["idempotent"] is True
+
+        r = await client.post(f"/fabric/graph-exports/{second_id}/activate")
+        assert r.status_code == 200, r.text
+        assert r.json()["previous_import_id"] == first_id
+        assert (await client.get("/fabric/graph/summary")).json()["node_count"] == 4
+
     async def test_read_only_queries_filter_graph_without_mutating_state_hub_entities(self, client):
         await _create_domain(client)
         topic = await _create_topic(client)