fix(governance): stabilize adr100 km growth slo

apps/api/tests/test_governance_agent.py

@@ -654,6 +654,7 @@ class _FakePrometheusResponse:
 class _FakePrometheusClient:
     def __init__(self, value: str) -> None:
         self._value = value
+        self.queries: list[str] = []
 
     async def __aenter__(self):
         return self
@@ -662,6 +663,7 @@ class _FakePrometheusClient:
         return False
 
     async def get(self, *args, **kwargs):  # noqa: ANN002, ANN003
+        self.queries.append(str(kwargs.get("params", {}).get("query", "")))
         return _FakePrometheusResponse(self._value)
 
 
@@ -683,3 +685,16 @@ class TestCheckSloCompliance:
             assert result[name]["status"] == "skipped"
             assert result[name]["reason"] == "prometheus_nan_or_inf"
         assert result["_meta"]["status"] == "no_data"
+
+    @pytest.mark.asyncio
+    async def test_km_growth_prefers_db_derived_24h_gauge(self):
+        """KM SLO 要優先使用 DB 24h gauge，避免新 counter 暖機時誤報 0."""
+        agent = _make_agent()
+        client = _FakePrometheusClient("25")
+
+        with patch("httpx.AsyncClient", return_value=client):
+            result = await agent.check_slo_compliance()
+
+        assert "max(knowledge_entries_created_24h) or sli:km_growth_rate:24h" in client.queries
+        assert result["km_growth_rate"]["status"] == "ok"
+        assert result["km_growth_rate"]["value"] == 25