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.IntegrationTests/DL205/DL205CoilMappingTests.cs

@@ -15,6 +15,7 @@ namespace ZB.MOM.WW.OtOpcUa.Driver.Modbus.IntegrationTests.DL205;
 public sealed class DL205CoilMappingTests(ModbusSimulatorFixture sim)
 {
     /// <summary>Verifies that DirectLOGIC Y0 output maps to Modbus coil 2048.</summary>
+    /// <returns>A task that represents the asynchronous test.</returns>
     [Fact]
     public async Task DL260_Y0_maps_to_coil_2048()
     {
@@ -42,6 +43,7 @@ public sealed class DL205CoilMappingTests(ModbusSimulatorFixture sim)
     }
 
     /// <summary>Verifies that DirectLOGIC C0 relay maps to Modbus coil 3072.</summary>
+    /// <returns>A task that represents the asynchronous test.</returns>
     [Fact]
     public async Task DL260_C0_maps_to_coil_3072()
     {
@@ -69,6 +71,7 @@ public sealed class DL205CoilMappingTests(ModbusSimulatorFixture sim)
     }
 
     /// <summary>Verifies that a scratch DirectLOGIC C relay supports write and read operations.</summary>
+    /// <returns>A task that represents the asynchronous test.</returns>
     [Fact]
     public async Task DL260_scratch_Crelay_supports_write_then_read()
     {