Add documentation comment for VersionHeightOffset property

Co-authored-by: AArnott <[email protected]>

Author: Copilot

src/NerdBank.GitVersioning/VersionOracle.cs

@@ -306,6 +306,12 @@ public string PrereleaseVersion
     /// when calculating the integer to use as the <see cref="BuildNumber"/>
     /// or elsewhere that the {height} macro is used.
     /// </summary>
+    /// <remarks>
+    /// This property returns the effective version height offset, which takes into account
+    /// the <see cref="VersionOptions.VersionHeightOffsetAppliesTo"/> property. If that property
+    /// is set and the version has changed such that the version height would be reset, this
+    /// will return 0 instead of the configured offset.
+    /// </remarks>
     public int VersionHeightOffset => this.VersionOptions?.EffectiveVersionHeightOffset ?? 0;
 
     /// <summary>