fix(etl): address Codex MCP review findings for Phase 2

- Filter MERGE SQL columns to only include columns that exist in destination
  (allColumns and updateColumns were using unfiltered source columns)
- Fix schema-qualified table names to use proper [schema].[table] format
  instead of wrapping entire name in single brackets
- Add empty column mapping validation to throw early if no columns intersect
- Add JdeDateTransformer output column collision detection in OnInitialize
- Add TODO comment for WithCommandTimeout (stored but not yet passed to
  destinations)
- Add tests for FormatQualifiedTableName and output column collision

NEW/tests/JdeScoping.DataSync.Tests/Etl/Scripts/CommonScriptsTests.cs

@@ -98,4 +98,20 @@ public class CommonScriptsTests
         Assert.Equal("TimeoutScript", runner.ScriptName);
         Assert.NotNull(runner);
     }
+
+    [Theory]
+    [InlineData("WorkOrder", "[dbo].[WorkOrder]")]
+    [InlineData("dbo.WorkOrder", "[dbo].[WorkOrder]")]
+    [InlineData("[dbo].[WorkOrder]", "[dbo].[WorkOrder]")]
+    [InlineData("Config.Settings", "[Config].[Settings]")]
+    [InlineData("[Config].[Settings]", "[Config].[Settings]")]
+    [InlineData("myschema.MyTable", "[myschema].[MyTable]")]
+    public void FormatQualifiedTableName_VariousFormats_FormatsCorrectly(string input, string expected)
+    {
+        // Act
+        var result = CommonScripts.FormatQualifiedTableName(input);
+
+        // Assert
+        Assert.Equal(expected, result);
+    }
 }