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/ModbusSubscriptionTests.cs

@@ -18,14 +18,10 @@ public sealed class ModbusSubscriptionTests
     private sealed class FakeTransport : IModbusTransport
     {
         public readonly ushort[] HoldingRegisters = new ushort[256];
-        /// <summary>Simulates connecting to the Modbus device.</summary>
-        /// <param name="ct">The cancellation token.</param>
+        /// <inheritdoc />
         public Task ConnectAsync(CancellationToken ct) => Task.CompletedTask;
 
-        /// <summary>Simulates sending a Modbus PDU.</summary>
-        /// <param name="unitId">The Modbus unit ID.</param>
-        /// <param name="pdu">The protocol data unit.</param>
-        /// <param name="ct">The cancellation token.</param>
+        /// <inheritdoc />
         public Task<byte[]> SendAsync(byte unitId, byte[] pdu, CancellationToken ct)
         {
             if (pdu[0] != 0x03) return Task.FromException<byte[]>(new NotSupportedException("FC not supported"));
@@ -41,7 +37,8 @@ public sealed class ModbusSubscriptionTests
             }
             return Task.FromResult(resp);
         }
-        /// <summary>Disposes the transport asynchronously.</summary>
+        /// <summary>Disposes the fake transport. No-op in this test double.</summary>
+        /// <returns>A completed value task.</returns>
         public ValueTask DisposeAsync() => ValueTask.CompletedTask;
     }
 
@@ -53,6 +50,7 @@ public sealed class ModbusSubscriptionTests
     }
 
     /// <summary>Verifies initial poll raises OnDataChange for every subscribed tag.</summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task Initial_poll_raises_OnDataChange_for_every_subscribed_tag()
     {
@@ -75,6 +73,7 @@ public sealed class ModbusSubscriptionTests
     }
 
     /// <summary>Verifies unchanged values do not raise after initial poll.</summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task Unchanged_values_do_not_raise_after_initial_poll()
     {
@@ -93,6 +92,7 @@ public sealed class ModbusSubscriptionTests
     }
 
     /// <summary>Verifies value change between polls raises OnDataChange.</summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task Value_change_between_polls_raises_OnDataChange()
     {
@@ -114,6 +114,7 @@ public sealed class ModbusSubscriptionTests
     }
 
     /// <summary>Verifies unsubscribe stops the polling loop.</summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task Unsubscribe_stops_the_polling_loop()
     {
@@ -134,6 +135,7 @@ public sealed class ModbusSubscriptionTests
     }
 
     /// <summary>Verifies SubscribeAsync floors intervals below 100ms.</summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task SubscribeAsync_floors_intervals_below_100ms()
     {
@@ -154,6 +156,7 @@ public sealed class ModbusSubscriptionTests
     }
 
     /// <summary>Verifies multiple subscriptions fire independently.</summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task Multiple_subscriptions_fire_independently()
     {
@@ -196,6 +199,7 @@ public sealed class ModbusSubscriptionTests
     ///     value steps up by 5 every poll (well over the deadband of 2) so every poll publishes,
     ///     maximising contention on the cache.
     /// </summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task Concurrent_deadband_subscriptions_do_not_corrupt_the_publish_cache()
     {