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/OpcUaClientSubscribeAndProbeTests.cs

@@ -13,6 +13,7 @@ namespace ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient.Tests;
 [Trait("Category", "Unit")]
 public sealed class OpcUaClientSubscribeAndProbeTests
 {
+    /// <summary>Verifies that subscribe without initialization throws InvalidOperationException.</summary>
     [Fact]
     public async Task SubscribeAsync_without_initialize_throws_InvalidOperationException()
     {
@@ -21,6 +22,7 @@ public sealed class OpcUaClientSubscribeAndProbeTests
             await drv.SubscribeAsync(["ns=2;s=Demo"], TimeSpan.FromMilliseconds(100), TestContext.Current.CancellationToken));
     }
 
+    /// <summary>Verifies that unsubscribe with unknown handle is a no-op.</summary>
     [Fact]
     public async Task UnsubscribeAsync_with_unknown_handle_is_noop()
     {
@@ -30,6 +32,7 @@ public sealed class OpcUaClientSubscribeAndProbeTests
         await drv.UnsubscribeAsync(new FakeHandle(), TestContext.Current.CancellationToken);
     }
 
+    /// <summary>Verifies that GetHostStatuses returns endpoint URL row before initialization.</summary>
     [Fact]
     public void GetHostStatuses_returns_endpoint_url_row_pre_init()
     {
@@ -43,8 +46,10 @@ public sealed class OpcUaClientSubscribeAndProbeTests
         rows[0].State.ShouldBe(HostState.Unknown);
     }
 
+    /// <summary>A fake subscription handle for testing.</summary>
     private sealed class FakeHandle : ISubscriptionHandle
     {
+        /// <inheritdoc />
         public string DiagnosticId => "fake";
     }
 }