docs: backfill XML documentation across 756 files

Adds <summary>, <param>, <typeparam>, and <inheritdoc/> tags to public
members surfaced by commentchecker — resolves 5,847 of 5,869 issues
(99.6%) across three /fixdocs passes.

tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Modbus.Tests/ModbusMultiUnitTests.cs

@@ -14,7 +14,13 @@ 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>
         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>
         public Task<byte[]> SendAsync(byte unitId, byte[] pdu, CancellationToken ct)
         {
             SeenUnitIds.Add(unitId);
@@ -30,9 +36,11 @@ public sealed class ModbusMultiUnitTests
                 default: return Task.FromResult(new byte[] { pdu[0], 0, 0 });
             }
         }
+        /// <summary>Disposes the transport resources.</summary>
         public ValueTask DisposeAsync() => ValueTask.CompletedTask;
     }
 
+    /// <summary>Verifies that per-tag UnitId routes reads to the correct slave.</summary>
     [Fact]
     public async Task PerTag_UnitId_Routes_To_Correct_Slave_In_MBAP()
     {
@@ -52,6 +60,7 @@ public sealed class ModbusMultiUnitTests
         fake.SeenUnitIds.ShouldNotContain((byte)99);
     }
 
+    /// <summary>Verifies that tags without UnitId override use the driver-level UnitId.</summary>
     [Fact]
     public async Task Tag_Without_UnitId_Falls_Back_To_DriverLevel()
     {
@@ -67,6 +76,7 @@ public sealed class ModbusMultiUnitTests
         fake.SeenUnitIds.ShouldContain((byte)7);
     }
 
+    /// <summary>Verifies that IPerCallHostResolver returns per-slave host strings.</summary>
     [Fact]
     public async Task IPerCallHostResolver_Returns_Per_Slave_Host_String()
     {
@@ -86,6 +96,7 @@ public sealed class ModbusMultiUnitTests
         resolver.ResolveHost("S1Temp").ShouldNotBe(resolver.ResolveHost("S5Temp"));
     }
 
+    /// <summary>Verifies that IPerCallHostResolver falls back to hostname for unknown tags.</summary>
     [Fact]
     public async Task IPerCallHostResolver_Unknown_Tag_Falls_Back_To_HostName()
     {