docs: add missing XML doc comments across gateway, worker, and .NET client

Resolves 1113 documentation-completeness gaps flagged by CommentChecker
(MissingReturns, MissingInheritDoc, InheritDocMisused, MissingDoc,
MissingParam, RedundantInheritDoc) so the API surface is fully documented
and the analyzer scan is clean. Doc comments only; no code changes.

clients/dotnet/ZB.MOM.WW.MxGateway.Client.Tests/LazyBrowseNodeTests.cs

@@ -12,6 +12,7 @@ public sealed class LazyBrowseNodeTests
     /// Verifies that calling BrowseAsync with no parent returns the root nodes
     /// from the first BrowseChildren reply and surfaces the per-child has-children hint.
     /// </summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task Browse_NoParent_ReturnsRoots()
     {
@@ -36,6 +37,7 @@ public sealed class LazyBrowseNodeTests
     /// <summary>
     /// Verifies that ExpandAsync populates Children and marks the node expanded after one RPC.
     /// </summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task Expand_PopulatesChildrenAndMarksExpanded()
     {
@@ -62,6 +64,7 @@ public sealed class LazyBrowseNodeTests
     /// <summary>
     /// Verifies that a second ExpandAsync call is a no-op and issues no additional RPC.
     /// </summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task Expand_CalledTwice_NoSecondRpc()
     {
@@ -86,6 +89,7 @@ public sealed class LazyBrowseNodeTests
     /// <summary>
     /// Verifies that an RPC failure (NotFound) during expand is wrapped in MxGatewayException.
     /// </summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task Expand_UnknownParent_ThrowsMxGatewayException()
     {
@@ -113,6 +117,7 @@ public sealed class LazyBrowseNodeTests
     /// <summary>
     /// Verifies that ExpandAsync drains multi-page sibling replies and forwards the page token.
     /// </summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task Expand_MultiPageSiblings_GathersAllPages()
     {
@@ -147,6 +152,7 @@ public sealed class LazyBrowseNodeTests
     /// <summary>
     /// Verifies that ten concurrent ExpandAsync calls issue exactly one RPC, not ten.
     /// </summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task Expand_CalledConcurrently_OnlyFiresOneRpc()
     {
@@ -178,6 +184,7 @@ public sealed class LazyBrowseNodeTests
     /// <summary>
     /// Verifies that BrowseChildrenOptions filter fields are forwarded to the BrowseChildren request.
     /// </summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task Browse_WithFilter_ForwardsToRequest()
     {