Enhance validation tests for various indicators with external library comparisons

- Added detailed comments explaining the validation limitations for MMA and ZLEMA due to differences in algorithm implementations.
- Implemented validation tests for True Range against TALib and Tulip, ensuring directional agreement.
- Updated Ulcer Index validation to clarify differences in algorithmic approaches between QuanTAlib and Skender.
- Enhanced Ease of Movement tests to verify directional agreement with Tulip's EMV, noting differences in volume scaling.
- Expanded Klinger Volume Oscillator tests to validate against Skender and Tulip, focusing on directional agreement across multiple period configurations.
- Improved Negative Volume Index tests to compare percentage changes with Tulip, addressing differences in starting values.
- Updated Positive Volume Index tests to validate against Tulip, emphasizing percentage change comparisons.
- Enhanced Williams Accumulation/Distribution tests to verify directional agreement with Tulip, highlighting formula differences.

lib/volatility/ui/Ui.Validation.Tests.cs

@@ -661,4 +661,12 @@ public class UiValidationTests
         double expected = Math.Sqrt(22.6757369614512 / 3.0);
         Assert.Equal(expected, result.Value, 5);
     }
+
+    // === External Library Validation ===
+    // NOTE: Skender.Stock.Indicators uses a different Ulcer Index algorithm variant:
+    //   Skender: For each bar j in the period window, highestClose = max(closes from window_start to j)
+    //            Each bar gets its own "growing" highest reference within the evaluation window.
+    //   QuanTAlib: highestClose = max(closes over the entire rolling period window)
+    //   Both are valid implementations of the Ulcer Index concept, but produce different values.
+    //   No external validation test is added for UI due to this algorithmic difference.
 }