test(historian): pin Uncertain-input degradation (T1 review)

Two Sql.Common tests close review finding I-1: an Uncertain NEXT neighbour makes an AtTime
interpolation Uncertain, and an Uncertain (non-Bad) sample in a bucket makes the aggregate
Uncertain. Each falsified with the reviewer's surviving mutation.

Claude-Session: https://claude.ai/code/session_01Ef2ozxS7QPanGT8uoATbTe

tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.Sql.Common.Tests/AggregateEvaluatorTests.cs

@@ -119,4 +119,14 @@ public sealed class AggregateEvaluatorTests
             AggregateEvaluator.Evaluate(HistoryAggregateType.TimeAverage, RowsA()[0], At(0), Now));
         ex.Aggregate.ShouldBe(HistoryAggregateType.TimeAverage);
     }
+
+    [Fact]
+    public void An_uncertain_sample_in_a_bucket_degrades_the_aggregate_to_uncertain()
+    {
+        // Two usable samples, one Good and one Uncertain, no Bad: the value is computed, the status is Uncertain.
+        var row = new BucketRow { Total = 2, Usable = 2, Good = 1, Bad = 0, Avg = 15, Min = 10, Max = 20, Sum = 30 };
+        var avg = AggregateEvaluator.Evaluate(HistoryAggregateType.Average, row, At(0), Now);
+        avg.Value.ShouldBe(15d);
+        avg.StatusCode.ShouldBe(UncertainCalc);
+    }
 }

tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.Sql.Common.Tests/AtTimeEvaluatorTests.cs

@@ -106,4 +106,13 @@ public sealed class AtTimeEvaluatorTests
         r.Value.ShouldBe("a");
         r.StatusCode.ShouldBe(Uncertain | 0x402u);
     }
+
+    [Fact]
+    public void An_uncertain_next_neighbour_makes_the_interpolation_uncertain()
+    {
+        var r = AtTimeEvaluator.Evaluate(At(5), S(0, HistorianValue.FromDouble(10), Good),
+            S(10, HistorianValue.FromDouble(20), Uncertain), Now, Now);
+        r.Value.ShouldBe(15d);
+        r.StatusCode.ShouldBe(UncertainInterpolated);
+    }
 }