fix(scada): preserve observation fields in chart evidence

tests/unit/test_scada_presentation_coverage.py

@@ -1,5 +1,6 @@
 """SCADA display coverage is independent of whether a device supports a conclusion."""
 from datetime import datetime, timedelta, timezone
+from copy import deepcopy
 from uuid import uuid4
 
 import pytest
@@ -16,6 +17,44 @@ END = datetime(2026, 7, 16, tzinfo=timezone.utc)
 START = END - timedelta(hours=3)
 
 
+@pytest.mark.anyio
+async def test_value_only_detail_evidence_cannot_claim_missing_observations():
+    from app.services.scada_presentation_coverage import verify_chart
+    task, repository, _, evidence_id = await investigation()
+    detail = deepcopy(repository.evidence[evidence_id])
+    detail["evidence_id"] = "detail-values"
+    rows = detail["data_snapshot"]["data"]["data"]["readings"]
+    detail["data_snapshot"]["data"]["data"] = [
+        {"device_id": row["device_id"], "time": row["time"], "value": row["monitored_value"]}
+        for row in rows
+    ]
+    value = chart(devices=["524529"])
+    value["series"][0].update(data=[None] * 13, sample_times=[None] * 13)
+    with pytest.raises(DomainError) as failure:
+        verify_chart(task, value, [repository.evidence[evidence_id], detail], ["detail-values"])
+    assert failure.value.code == "SCADA_CHART_EVIDENCE_REQUIRED"
+
+
+@pytest.mark.anyio
+@pytest.mark.parametrize("field", ["monitored_value", "cleaned_value"])
+async def test_detail_fields_do_not_discard_other_observed_fields(field):
+    from app.services.scada_presentation_coverage import verify_chart
+    task, repository, _, evidence_id = await investigation()
+    detail = deepcopy(repository.evidence[evidence_id])
+    detail["evidence_id"] = "detail-cleaned"
+    rows = detail["data_snapshot"]["data"]["data"]["readings"]
+    detail["data_snapshot"]["data"]["data"] = [
+        {"device_id": row["device_id"], "time": row["time"], "value": row["cleaned_value"] + 10,
+         "cleaned_value": row["cleaned_value"] + 10} for row in rows
+    ]
+    value = chart(devices=["524529"])
+    value["scada"]["value_field"] = field
+    if field == "cleaned_value":
+        value["series"][0]["data"] = [point + 10 for point in value["series"][0]["data"]]
+    result = verify_chart(task, value, [repository.evidence[evidence_id], detail], [evidence_id, "detail-cleaned"])
+    assert result["gaps"] == []
+
+
 @pytest.fixture
 def anyio_backend():
     return "asyncio"