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/OpcUaClientLowFindingsRegressionTests.cs

@@ -121,6 +121,7 @@ public sealed class OpcUaClientLowFindingsRegressionTests
     }
 
     /// <summary>Verifies that UnsubscribeAsync with unknown handle does not throw after the fix.</summary>
+    /// <returns>A task that represents the asynchronous test operation.</returns>
     [Fact]
     public async Task UnsubscribeAsync_unknown_handle_does_not_throw_after_fix()
     {
@@ -132,6 +133,7 @@ public sealed class OpcUaClientLowFindingsRegressionTests
     }
 
     /// <summary>Verifies that UnsubscribeAlarmsAsync with unknown handle does not throw after the fix.</summary>
+    /// <returns>A task that represents the asynchronous test operation.</returns>
     [Fact]
     public async Task UnsubscribeAlarmsAsync_unknown_handle_does_not_throw_after_fix()
     {
@@ -143,14 +145,14 @@ public sealed class OpcUaClientLowFindingsRegressionTests
     /// <summary>Fake subscription handle for testing.</summary>
     private sealed class FakeHandle : Core.Abstractions.ISubscriptionHandle
     {
-        /// <summary>Gets the diagnostic identifier for this handle.</summary>
+        /// <inheritdoc />
         public string DiagnosticId => "fake-sub";
     }
 
     /// <summary>Fake alarm subscription handle for testing.</summary>
     private sealed class FakeAlarmHandle : Core.Abstractions.IAlarmSubscriptionHandle
     {
-        /// <summary>Gets the diagnostic identifier for this handle.</summary>
+        /// <inheritdoc />
         public string DiagnosticId => "fake-alarm-sub";
     }
 }