fix(km): retry transient list readbacks

apps/api/tests/test_knowledge_service_readback_degraded.py

@@ -1,5 +1,6 @@
 import pytest
 
+from src.models.knowledge import KnowledgeListResponse
 from src.services import knowledge_service as knowledge_service_module
 from src.services.knowledge_service import KnowledgeService
 
@@ -85,6 +86,28 @@ async def test_knowledge_list_entries_source_backed_filter_and_search(monkeypatc
     assert response.asset_taxonomy[[row.key for row in response.asset_taxonomy].index("alert")].count == 1
 
 
+@pytest.mark.asyncio
+async def test_knowledge_list_entries_retries_transient_pool_timeout(monkeypatch) -> None:
+    service = KnowledgeService.__new__(KnowledgeService)
+    calls = 0
+
+    async def fake_primary(**_kwargs):
+        nonlocal calls
+        calls += 1
+        if calls == 1:
+            raise RuntimeError("db pool exhausted")
+        return KnowledgeListResponse(items=[], total=1, readback_status="ready")
+
+    monkeypatch.setattr(service, "_list_entries_from_primary", fake_primary)
+
+    response = await service.list_entries(limit=50)
+
+    assert calls == 2
+    assert response.readback_status == "ready"
+    assert response.primary_readback_ready is True
+    assert response.operator_stage == "knowledge_readback_primary_retry_recovered"
+
+
 @pytest.mark.asyncio
 async def test_knowledge_search_fails_soft_to_source_backed_entries(monkeypatch) -> None:
     monkeypatch.setattr(