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/OpcUaClientFailoverTests.cs

@@ -7,6 +7,7 @@ namespace ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient.Tests;
 [Trait("Category", "Unit")]
 public sealed class OpcUaClientFailoverTests
 {
+    /// <summary>Verifies that ResolveEndpointCandidates prefers EndpointUrls when provided.</summary>
     [Fact]
     public void ResolveEndpointCandidates_prefers_EndpointUrls_when_provided()
     {
@@ -21,6 +22,7 @@ public sealed class OpcUaClientFailoverTests
         list[1].ShouldBe("opc.tcp://backup:4841");
     }
 
+    /// <summary>Verifies that ResolveEndpointCandidates falls back to single EndpointUrl when list is empty.</summary>
     [Fact]
     public void ResolveEndpointCandidates_falls_back_to_single_EndpointUrl_when_list_empty()
     {
@@ -30,6 +32,7 @@ public sealed class OpcUaClientFailoverTests
         list[0].ShouldBe("opc.tcp://only:4840");
     }
 
+    /// <summary>Verifies that an empty EndpointUrls list is treated as a fallback to EndpointUrl.</summary>
     [Fact]
     public void ResolveEndpointCandidates_empty_list_treated_as_fallback_to_EndpointUrl()
     {
@@ -43,6 +46,7 @@ public sealed class OpcUaClientFailoverTests
         OpcUaClientDriver.ResolveEndpointCandidates(opts).Count.ShouldBe(1);
     }
 
+    /// <summary>Verifies that HostName uses the first candidate before connection.</summary>
     [Fact]
     public void HostName_uses_first_candidate_before_connect()
     {
@@ -55,6 +59,7 @@ public sealed class OpcUaClientFailoverTests
             "pre-connect the dashboard should show the first candidate URL so operators can link back");
     }
 
+    /// <summary>Verifies that initializing against all unreachable endpoints throws AggregateException listing each.</summary>
     [Fact]
     public async Task Initialize_against_all_unreachable_endpoints_throws_AggregateException_listing_each()
     {