docs: backfill XML documentation across 756 files

Adds <summary>, <param>, <typeparam>, and <inheritdoc/> tags to public
members surfaced by commentchecker — resolves 5,847 of 5,869 issues
(99.6%) across three /fixdocs passes.

tests/Client/ZB.MOM.WW.OtOpcUa.Client.Shared.Tests/Helpers/SecurityModeMapperTests.cs

@@ -8,6 +8,9 @@ namespace ZB.MOM.WW.OtOpcUa.Client.Shared.Tests.Helpers;
 
 public class SecurityModeMapperTests
 {
+    /// <summary>Verifies ToMessageSecurityMode correctly maps SecurityMode values to OPC UA MessageSecurityMode.</summary>
+    /// <param name="input">The SecurityMode value to map.</param>
+    /// <param name="expected">The expected MessageSecurityMode result.</param>
     [Theory]
     [InlineData(SecurityMode.None, MessageSecurityMode.None)]
     [InlineData(SecurityMode.Sign, MessageSecurityMode.Sign)]
@@ -17,6 +20,7 @@ public class SecurityModeMapperTests
         SecurityModeMapper.ToMessageSecurityMode(input).ShouldBe(expected);
     }
 
+    /// <summary>Verifies ToMessageSecurityMode throws on invalid SecurityMode values.</summary>
     [Fact]
     public void ToMessageSecurityMode_InvalidValue_Throws()
     {
@@ -24,6 +28,9 @@ public class SecurityModeMapperTests
             SecurityModeMapper.ToMessageSecurityMode((SecurityMode)99));
     }
 
+    /// <summary>Verifies FromString correctly parses security mode strings (case-insensitive).</summary>
+    /// <param name="input">The security mode string to parse.</param>
+    /// <param name="expected">The expected SecurityMode result.</param>
     [Theory]
     [InlineData("none", SecurityMode.None)]
     [InlineData("None", SecurityMode.None)]
@@ -38,18 +45,21 @@ public class SecurityModeMapperTests
         SecurityModeMapper.FromString(input).ShouldBe(expected);
     }
 
+    /// <summary>Verifies FromString correctly parses strings with leading and trailing whitespace.</summary>
     [Fact]
     public void FromString_WithWhitespace_ParsesCorrectly()
     {
         SecurityModeMapper.FromString("  sign  ").ShouldBe(SecurityMode.Sign);
     }
 
+    /// <summary>Verifies FromString throws on unrecognized security mode strings.</summary>
     [Fact]
     public void FromString_UnknownValue_Throws()
     {
         Should.Throw<ArgumentException>(() => SecurityModeMapper.FromString("invalid"));
     }
 
+    /// <summary>Verifies FromString returns None when passed a null string.</summary>
     [Fact]
     public void FromString_Null_DefaultsToNone()
     {