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.FOCAS.Tests/FocasLoggingTests.cs

@@ -31,6 +31,7 @@ public sealed class FocasLoggingTests
     }
 
     /// <summary>Verifies that probe loop logs when an exception is swallowed.</summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task ProbeLoop_logs_when_an_exception_is_swallowed()
     {
@@ -90,9 +91,11 @@ public sealed class FocasLoggingTests
         /// <summary>Begins a logging scope.</summary>
         /// <param name="state">The scope state.</param>
         /// <typeparam name="TState">The type of the state.</typeparam>
+        /// <returns>A disposable scope object.</returns>
         public IDisposable BeginScope<TState>(TState state) where TState : notnull => NullScope.Instance;
         /// <summary>Checks if logging is enabled for the specified level.</summary>
         /// <param name="logLevel">The log level.</param>
+        /// <returns><c>true</c> if logging is enabled for <paramref name="logLevel"/>; otherwise, <c>false</c>.</returns>
         public bool IsEnabled(LogLevel logLevel) => true;
         /// <summary>Logs a message.</summary>
         /// <param name="logLevel">The log level.</param>