feat(etl): add MapOrdinal override to ColumnDropTransformer

NEW/src/JdeScoping.DataSync/Etl/Transformers/ColumnDropTransformer.cs

@@ -63,4 +63,7 @@ public class ColumnDropTransformer : DataTransformerBase
 
     /// <inheritdoc />
     public override bool IsDBNull(int ordinal, IDataReader source) => source.IsDBNull(_ordinalMap![ordinal]);
+
+    /// <inheritdoc />
+    public override int MapOrdinal(int transformedOrdinal, IDataReader source) => _ordinalMap![transformedOrdinal];
 }

NEW/tests/JdeScoping.DataSync.Tests/Etl/Transformers/ColumnDropTransformerTests.cs

@@ -71,6 +71,21 @@ public class ColumnDropTransformerTests
         Assert.Equal("Value", reader.GetName(2));
     }
 
+    [Fact]
+    public void MapOrdinal_DroppedColumn_MapsCorrectly()
+    {
+        // Arrange - drop column B (ordinal 1), so C becomes ordinal 1
+        var source = CreateMockReader(new[] { "A", "B", "C" });
+        var transformer = new ColumnDropTransformer("B");
+        transformer.Transform(source);
+
+        // Act - transformed ordinal 1 should map to source ordinal 2 (C)
+        var result = transformer.MapOrdinal(1, source);
+
+        // Assert
+        Assert.Equal(2, result);
+    }
+
     private static IDataReader CreateMockReader(string[] columns, object[]? values = null)
     {
         var reader = Substitute.For<IDataReader>();