chore: repo cleanup and code quality improvements

- Remove global.json (SDK pinning unnecessary)

- Remove nuget.config, move MyGet source to .csproj RestoreAdditionalProjectSources

- Gitignore ndepend/ entirely, move badges to docs/img/

- Update README.md and docs/ndepend.md badge paths

- Add NDepend project property to QuanTAlib.slnx

- Expand .editorconfig ReSharper/diagnostic suppressions

- Use ArgumentOutOfRangeException instead of ArgumentException

- Use discard _ for unused event sender parameters

- Remove quantalib.code-workspace and sonar-suppressions.json

- Add filter signature SVGs

lib/statistics/spearman/Spearman.cs

@@ -98,15 +98,11 @@ public sealed class Spearman : AbstractBase
     {
         return Update(new TValue(DateTime.UtcNow, seriesX), new TValue(DateTime.UtcNow, seriesY), isNew);
     }
-
-    /// <inheritdoc/>
     /// <remarks>Not supported for dual-input indicator. Use Update(seriesX, seriesY) instead.</remarks>
     public override TValue Update(TValue input, bool isNew = true)
     {
         throw new NotSupportedException("Spearman requires two inputs (seriesX and seriesY). Use Update(seriesX, seriesY).");
     }
-
-    /// <inheritdoc/>
     /// <remarks>Not supported for dual-input indicator. Use Batch(seriesX, seriesY, period) instead.</remarks>
     public override TSeries Update(TSeries source)
     {
@@ -236,8 +232,6 @@ public sealed class Spearman : AbstractBase
             ranks[i] = countSmaller + (countEqual - 1) * 0.5 + 1.0;
         }
     }
-
-    /// <inheritdoc/>
     public override void Prime(ReadOnlySpan<double> source, TimeSpan? step = null)
     {
         throw new NotSupportedException("Spearman requires two inputs.");