docs: complete XML doc comments via fixdocs (2757 to 131 findings)

Add missing <returns>/<param>/<summary>/<typeparam> tags and clean up
misused inheritdoc across 481 files so the documented API surface is
complete. Documentation-only (zero code lines changed). The 131 remaining
findings are inheritdoc-style warnings deliberately left to preserve
hand-written implementation rationale (plan-decision notes, race-condition
explanations).

tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient.Browser.Tests/OpcUaClientBrowseSessionTests.cs

@@ -37,6 +37,7 @@ public sealed class OpcUaClientBrowseSessionTests
 
     /// <summary>RootAsync should surface at least one node under ObjectsFolder
     /// (opc-plc exposes a non-empty top level).</summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task RootAsync_returns_at_least_one_node()
     {
@@ -49,6 +50,7 @@ public sealed class OpcUaClientBrowseSessionTests
 
     /// <summary>ExpandAsync should accept a stable NodeId returned by RootAsync
     /// and round-trip through the live namespace table.</summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task ExpandAsync_round_trips_stable_NodeId()
     {
@@ -64,6 +66,7 @@ public sealed class OpcUaClientBrowseSessionTests
 
     /// <summary>The OPC UA picker treats variables as terminal leaves, so
     /// AttributesAsync must always be empty for this driver.</summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task AttributesAsync_is_empty_for_opcuaclient()
     {