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/Server/ZB.MOM.WW.OtOpcUa.AdminUI.Tests/ModbusDriverPageFormSerializationTests.cs

@@ -21,6 +21,7 @@ public sealed class ModbusDriverPageFormSerializationTests
         UnmappedMemberHandling = JsonUnmappedMemberHandling.Skip,
     };
 
+    /// <summary>Verifies that round-trip serialization preserves all known Modbus driver fields.</summary>
     [Fact]
     public void RoundTrip_PreservesKnownFields()
     {
@@ -97,6 +98,7 @@ public sealed class ModbusDriverPageFormSerializationTests
         back.ProbeTimeoutSeconds.ShouldBe(10);
     }
 
+    /// <summary>Verifies that deserialization silently drops unknown Modbus driver fields.</summary>
     [Fact]
     public void Deserialize_DropsUnknownFields()
     {
@@ -112,6 +114,7 @@ public sealed class ModbusDriverPageFormSerializationTests
         back.ProbeTimeoutSeconds.ShouldBe(10);
     }
 
+    /// <summary>Verifies that a tag row round-trips through its definition.</summary>
     [Fact]
     public void TagRow_round_trips_through_definition()
     {
@@ -129,6 +132,7 @@ public sealed class ModbusDriverPageFormSerializationTests
         back.Writable.ShouldBeTrue();
     }
 
+    /// <summary>Verifies that the tag list survives a full options serialization round-trip.</summary>
     [Fact]
     public void Tag_list_survives_options_serialize_round_trip()
     {
@@ -144,6 +148,7 @@ public sealed class ModbusDriverPageFormSerializationTests
         back.Tags[0].Name.ShouldBe("A");
     }
 
+    /// <summary>Verifies that tag row validation rejects a duplicate tag name.</summary>
     [Fact]
     public void ValidateRow_rejects_duplicate_name()
     {
@@ -152,6 +157,7 @@ public sealed class ModbusDriverPageFormSerializationTests
             .ShouldNotBeNull();
     }
 
+    /// <summary>Verifies that converting a tag row to a definition preserves unedited fields.</summary>
     [Fact]
     public void ToDefinition_preserves_unedited_fields()
     {