fix(scada): preserve observation fields in chart evidence

app/mcp/query_service.py

@@ -394,6 +394,9 @@ async def execute_query(
                 if hasattr(args, "field") and args.field not in units:
                     gaps.append(f"Unit metadata is unavailable for field {args.field}")
         else:
+            # Keep the selected field in durable evidence; `value` alone cannot
+            # distinguish raw observations from cleaned observations.
+            data = [{**row, args.field: row["value"]} if "value" in row else row for row in data]
             metadata = [
                 r
                 for device in ids

app/services/scada_presentation_coverage.py

@@ -77,7 +77,8 @@ class ScadaObservations:
                 if "time" in row and "device_id" in row:
                     at = datetime.fromisoformat(row["time"])
                     if start <= at <= end:
-                        self.values[(str(row["device_id"]), at)] = row
+                        observed = self.values.setdefault((str(row["device_id"]), at), {})
+                        observed.update({field: row[field] for field in ("monitored_value", "cleaned_value") if field in row})
 
     def absent_reason(self, device: str, at: datetime) -> str | None:
         for ids, outside, start, end in self.windows:
@@ -206,6 +207,8 @@ def verify_chart(task: dict, chart: dict, evidence: list[dict], refs: list[str])
                         "历史散点只保留每日末三个对应时刻")
                 continue
             record = observations.values.get((device, at))
+            require(record is None or field in record, "SCADA_CHART_EVIDENCE_REQUIRED",
+                    f"设备 {device} 的证据未标明 {field}，请重新读取明确的监测字段", refs=[device])
             actual = record.get(field) if record is not None else None
             if actual is None:
                 absent = observations.absent_reason(device, at)