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.TwinCAT.Tests/TwinCATNativeNotificationTests.cs

@@ -23,6 +23,7 @@ public sealed class TwinCATNativeNotificationTests
     }
 
     /// <summary>Verifies that native subscribe registers one notification per tag.</summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task Native_subscribe_registers_one_notification_per_tag()
     {
@@ -39,6 +40,7 @@ public sealed class TwinCATNativeNotificationTests
     }
 
     /// <summary>Verifies that native notification fires OnDataChange with pushed value.</summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task Native_notification_fires_OnDataChange_with_pushed_value()
     {
@@ -60,6 +62,7 @@ public sealed class TwinCATNativeNotificationTests
     }
 
     /// <summary>Verifies that native unsubscribe disposes all notifications.</summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task Native_unsubscribe_disposes_all_notifications()
     {
@@ -76,6 +79,7 @@ public sealed class TwinCATNativeNotificationTests
     }
 
     /// <summary>Verifies that native unsubscribe halts future notifications.</summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task Native_unsubscribe_halts_future_notifications()
     {
@@ -99,6 +103,7 @@ public sealed class TwinCATNativeNotificationTests
     }
 
     /// <summary>Verifies that native subscribe failure mid-registration cleans up partial state.</summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task Native_subscribe_failure_mid_registration_cleans_up_partial_state()
     {
@@ -157,6 +162,7 @@ public sealed class TwinCATNativeNotificationTests
     }
 
     /// <summary>Verifies that native shutdown disposes subscriptions.</summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task Native_shutdown_disposes_subscriptions()
     {
@@ -172,6 +178,7 @@ public sealed class TwinCATNativeNotificationTests
     }
 
     /// <summary>Verifies that the poll path still works when UseNativeNotifications is false.</summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task Poll_path_still_works_when_UseNativeNotifications_false()
     {
@@ -200,6 +207,7 @@ public sealed class TwinCATNativeNotificationTests
     }
 
     /// <summary>Verifies that subscribe handle DiagnosticId indicates native vs poll.</summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task Subscribe_handle_DiagnosticId_indicates_native_vs_poll()
     {