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/Mitsubishi/MitsubishiProfile.cs

@@ -26,6 +26,7 @@ public static class MitsubishiProfile
     /// <summary>Builds Modbus driver options configured for the Mitsubishi profile.</summary>
     /// <param name="host">The Modbus server hostname or IP address.</param>
     /// <param name="port">The Modbus server port number.</param>
+    /// <returns>A <see cref="ModbusDriverOptions"/> instance configured for the Mitsubishi profile.</returns>
     public static ModbusDriverOptions BuildOptions(string host, int port) => new()
     {
         Host = host,

tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Modbus.IntegrationTests/Mitsubishi/MitsubishiQuirkTests.cs

@@ -20,6 +20,7 @@ namespace ZB.MOM.WW.OtOpcUa.Driver.Modbus.IntegrationTests.Mitsubishi;
 public sealed class MitsubishiQuirkTests(ModbusSimulatorFixture sim)
 {
     /// <summary>Verifies that Mitsubishi D0 register fingerprint reads the expected value 0x1234.</summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task Mitsubishi_D0_fingerprint_reads_0x1234()
     {
@@ -36,6 +37,7 @@ public sealed class MitsubishiQuirkTests(ModbusSimulatorFixture sim)
     }
 
     /// <summary>Verifies that Mitsubishi Float32 with CDAB word order decodes correctly to 1.5 from D100.</summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task Mitsubishi_Float32_CDAB_decodes_1_5f_from_D100()
     {
@@ -62,6 +64,7 @@ public sealed class MitsubishiQuirkTests(ModbusSimulatorFixture sim)
     }
 
     /// <summary>Verifies that Mitsubishi D registers store binary values, not BCD.</summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task Mitsubishi_D10_is_binary_not_BCD()
     {
@@ -81,6 +84,7 @@ public sealed class MitsubishiQuirkTests(ModbusSimulatorFixture sim)
     }
 
     /// <summary>Verifies that reading a binary D register as BCD throws when the value contains non-decimal nibbles.</summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task Mitsubishi_D10_as_BCD_throws_because_nibble_is_non_decimal()
     {
@@ -102,6 +106,7 @@ public sealed class MitsubishiQuirkTests(ModbusSimulatorFixture sim)
     }
 
     /// <summary>Verifies that Mitsubishi Q/L/iQ-R X inputs use hex addressing and X210 maps correctly.</summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task Mitsubishi_QLiQR_X210_hex_maps_to_DI_528_reads_ON()
     {
@@ -134,6 +139,7 @@ public sealed class MitsubishiQuirkTests(ModbusSimulatorFixture sim)
     }
 
     /// <summary>Verifies that Mitsubishi M512 relay maps to coil address 512 and reads ON.</summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task Mitsubishi_M512_maps_to_coil_512_reads_ON()
     {

tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Modbus.IntegrationTests/Mitsubishi/MitsubishiSmokeTests.cs

@@ -16,6 +16,7 @@ namespace ZB.MOM.WW.OtOpcUa.Driver.Modbus.IntegrationTests.Mitsubishi;
 public sealed class MitsubishiSmokeTests(ModbusSimulatorFixture sim)
 {
     /// <summary>Verifies end-to-end write and read of a Mitsubishi holding register via the Modbus driver.</summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task Mitsubishi_roundtrip_write_then_read_of_holding_register()
     {