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.AbCip.Tests/AbCipAlarmProjectionTests.cs

@@ -49,6 +49,7 @@ public sealed class AbCipAlarmProjectionTests
     }
 
     /// <summary>Verifies that disabled alarm projection returns a valid handle but does not poll.</summary>
+    /// <returns>A task that represents the asynchronous test.</returns>
     [Fact]
     public async Task FeatureFlag_Off_SubscribeAlarms_Returns_Handle_But_Never_Polls()
     {
@@ -76,6 +77,7 @@ public sealed class AbCipAlarmProjectionTests
     }
 
     /// <summary>Verifies that enabled alarm projection starts polling and fires raise event on 0-to-1 transition.</summary>
+    /// <returns>A task that represents the asynchronous test.</returns>
     [Fact]
     public async Task FeatureFlag_On_Subscribe_Starts_Polling_And_Fires_Raise_On_0_to_1()
     {
@@ -120,6 +122,7 @@ public sealed class AbCipAlarmProjectionTests
     }
 
     /// <summary>Verifies that alarm clear event fires on 1-to-0 transition.</summary>
+    /// <returns>A task that represents the asynchronous test.</returns>
     [Fact]
     public async Task Clear_Event_Fires_On_1_to_0_Transition()
     {
@@ -161,6 +164,7 @@ public sealed class AbCipAlarmProjectionTests
     }
 
     /// <summary>Verifies that unsubscribing stops the alarm poll loop.</summary>
+    /// <returns>A task that represents the asynchronous test.</returns>
     [Fact]
     public async Task Unsubscribe_Stops_The_Poll_Loop()
     {