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.Modbus.Tests/ModbusProtocolOptionsTests.cs

@@ -15,15 +15,9 @@ public sealed class ModbusProtocolOptionsTests
     private sealed class CapturingTransport : IModbusTransport
     {
         public readonly List<byte[]> Sent = new();
-        /// <summary>Asynchronously connects the transport.</summary>
-        /// <param name="ct">The cancellation token.</param>
-        /// <returns>A completed task.</returns>
+        /// <inheritdoc />
         public Task ConnectAsync(CancellationToken ct) => Task.CompletedTask;
-        /// <summary>Asynchronously sends a Modbus PDU and returns a response.</summary>
-        /// <param name="unitId">The Modbus unit ID.</param>
-        /// <param name="pdu">The protocol data unit to send.</param>
-        /// <param name="ct">The cancellation token.</param>
-        /// <returns>A task that returns the response bytes.</returns>
+        /// <inheritdoc />
         public Task<byte[]> SendAsync(byte unitId, byte[] pdu, CancellationToken ct)
         {
             Sent.Add(pdu);
@@ -70,6 +64,7 @@ public sealed class ModbusProtocolOptionsTests
     }
 
     /// <summary>Verifies that single coil write uses FC05 by default.</summary>
+    /// <returns>A task that represents the asynchronous test operation.</returns>
     [Fact]
     public async Task Single_Coil_Write_Uses_FC05_By_Default()
     {
@@ -84,6 +79,7 @@ public sealed class ModbusProtocolOptionsTests
     }
 
     /// <summary>Verifies that single coil write uses FC15 when forced.</summary>
+    /// <returns>A task that represents the asynchronous test operation.</returns>
     [Fact]
     public async Task Single_Coil_Write_Uses_FC15_When_Forced()
     {
@@ -99,6 +95,7 @@ public sealed class ModbusProtocolOptionsTests
     }
 
     /// <summary>Verifies that single register write uses FC06 by default.</summary>
+    /// <returns>A task that represents the asynchronous test operation.</returns>
     [Fact]
     public async Task Single_Register_Write_Uses_FC06_By_Default()
     {
@@ -113,6 +110,7 @@ public sealed class ModbusProtocolOptionsTests
     }
 
     /// <summary>Verifies that single register write uses FC16 when forced.</summary>
+    /// <returns>A task that represents the asynchronous test operation.</returns>
     [Fact]
     public async Task Single_Register_Write_Uses_FC16_When_Forced()
     {
@@ -128,6 +126,7 @@ public sealed class ModbusProtocolOptionsTests
     }
 
     /// <summary>Verifies that coil array read automatically chunks at MaxCoilsPerRead.</summary>
+    /// <returns>A task that represents the asynchronous test operation.</returns>
     [Fact]
     public async Task Coil_Array_Read_Auto_Chunks_At_MaxCoilsPerRead()
     {