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.Tests/OpcUaClientSubscribeAndProbeTests.cs

@@ -14,6 +14,7 @@ namespace ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient.Tests;
 public sealed class OpcUaClientSubscribeAndProbeTests
 {
     /// <summary>Verifies that subscribe without initialization throws InvalidOperationException.</summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task SubscribeAsync_without_initialize_throws_InvalidOperationException()
     {
@@ -23,6 +24,7 @@ public sealed class OpcUaClientSubscribeAndProbeTests
     }
 
     /// <summary>Verifies that unsubscribe with unknown handle is a no-op.</summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task UnsubscribeAsync_with_unknown_handle_is_noop()
     {