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/Drivers/ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient.Tests/OpcUaClientCertAuthTests.cs

@@ -8,6 +8,9 @@ namespace ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient.Tests;
 [Trait("Category", "Unit")]
 public sealed class OpcUaClientCertAuthTests
 {
+    /// <summary>
+    /// Verifies that BuildCertificateIdentity rejects missing certificate path.
+    /// </summary>
     [Fact]
     public void BuildCertificateIdentity_rejects_missing_path()
     {
@@ -16,6 +19,9 @@ public sealed class OpcUaClientCertAuthTests
             .Message.ShouldContain("UserCertificatePath");
     }
 
+    /// <summary>
+    /// Verifies that BuildCertificateIdentity rejects nonexistent certificate file.
+    /// </summary>
     [Fact]
     public void BuildCertificateIdentity_rejects_nonexistent_file()
     {
@@ -27,6 +33,9 @@ public sealed class OpcUaClientCertAuthTests
         Should.Throw<FileNotFoundException>(() => OpcUaClientDriver.BuildCertificateIdentity(opts));
     }
 
+    /// <summary>
+    /// Verifies that BuildCertificateIdentity loads a valid PFX with private key.
+    /// </summary>
     [Fact]
     public void BuildCertificateIdentity_loads_a_valid_PFX_with_private_key()
     {