M42: calibrate grounded RAGcore fallback

backend/tests/test_knowledge.py

@@ -711,7 +711,7 @@ def test_ragcore_search_fallback_prefers_damage_procedure(monkeypatch):
     assert any(source.document_id == "damage-procedure" for source in answer.sources)
 
 
-def test_ragcore_search_fallback_accepts_relevant_damage_evidence_above_threshold(monkeypatch):
+def test_ragcore_search_fallback_accepts_top_ranked_ragcore_damage_evidence(monkeypatch):
     provider = RAGcoreKnowledgeProvider()
     monkeypatch.setattr(provider._settings, "ragcore_space_id", "space-1")
     search = _search_body()
@@ -725,7 +725,9 @@ def test_ragcore_search_fallback_accepts_relevant_damage_evidence_above_threshol
                 "excerpt": "Record damage and keep the vehicle blocked.",
             },
             "rank": 1,
-            "scores": {"fused": 0.5},
+            # RAGcore uses reciprocal-rank fusion; a genuine rank-one result is about
+            # 1 / (60 + 1), not a normalized 0..1 relevance score.
+            "scores": {"fused": 0.01639344262295082},
         }
     )
     monkeypatch.setattr(