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/ModbusMultiUnitTests.cs

@@ -14,13 +14,9 @@ public sealed class ModbusMultiUnitTests
     private sealed class UnitCapturingTransport : IModbusTransport
     {
         public readonly List<byte> SeenUnitIds = new();
-        /// <summary>Connects to the transport.</summary>
-        /// <param name="ct">Token to cancel the connection.</param>
+        /// <inheritdoc />
         public Task ConnectAsync(CancellationToken ct) => Task.CompletedTask;
-        /// <summary>Sends a Modbus PDU and returns a response.</summary>
-        /// <param name="unitId">The Modbus unit ID for the request.</param>
-        /// <param name="pdu">The protocol data unit to send.</param>
-        /// <param name="ct">Token to cancel the operation.</param>
+        /// <inheritdoc />
         public Task<byte[]> SendAsync(byte unitId, byte[] pdu, CancellationToken ct)
         {
             SeenUnitIds.Add(unitId);
@@ -36,11 +32,13 @@ public sealed class ModbusMultiUnitTests
                 default: return Task.FromResult(new byte[] { pdu[0], 0, 0 });
             }
         }
-        /// <summary>Disposes the transport resources.</summary>
+        /// <summary>Releases the transport; this implementation is a no-op.</summary>
+        /// <returns>A completed value task.</returns>
         public ValueTask DisposeAsync() => ValueTask.CompletedTask;
     }
 
     /// <summary>Verifies that per-tag UnitId routes reads to the correct slave.</summary>
+    /// <returns>A task that represents the asynchronous test operation.</returns>
     [Fact]
     public async Task PerTag_UnitId_Routes_To_Correct_Slave_In_MBAP()
     {
@@ -61,6 +59,7 @@ public sealed class ModbusMultiUnitTests
     }
 
     /// <summary>Verifies that tags without UnitId override use the driver-level UnitId.</summary>
+    /// <returns>A task that represents the asynchronous test operation.</returns>
     [Fact]
     public async Task Tag_Without_UnitId_Falls_Back_To_DriverLevel()
     {
@@ -77,6 +76,7 @@ public sealed class ModbusMultiUnitTests
     }
 
     /// <summary>Verifies that IPerCallHostResolver returns per-slave host strings.</summary>
+    /// <returns>A task that represents the asynchronous test operation.</returns>
     [Fact]
     public async Task IPerCallHostResolver_Returns_Per_Slave_Host_String()
     {
@@ -97,6 +97,7 @@ public sealed class ModbusMultiUnitTests
     }
 
     /// <summary>Verifies that IPerCallHostResolver falls back to hostname for unknown tags.</summary>
+    /// <returns>A task that represents the asynchronous test operation.</returns>
     [Fact]
     public async Task IPerCallHostResolver_Unknown_Tag_Falls_Back_To_HostName()
     {