Fix serializers

[wieslawsoltes]

PR Summary - Issue 924 Serialization Fixes

Findings

• XML serialization failed with a DataContractSerializer error when derived model types were marked with DataContract but their base types were not.
• Serializer coverage did not include full round-trip tests across all supported formats.
• System.Text.Json and YAML attempted to serialize interface-typed properties that should be ignored (for example ICommand or IgnoreDataMember), causing deserialization failures.
• YAML could not hydrate interface-typed collections because type tags were missing.
• Protobuf lacked a stable model for interface-heavy graphs and had no explicit member registration for DataMember-only models, leading to missing or defaulted data.

Implementation

• DataContract alignment
  • Removed DataContract attributes from derived model implementations that inherit non-DataContract bases.
  • Added DataContract(IsReference = true) to base ReactiveBase types so derived models remain DataContract-compatible.
  • Relaxed DockWindow DataMember requirements on geometry fields so IsReference works without required members.
• XML serializer
  • Built known types via reflection, filtered to public, non-abstract dock types, and validated DataContract compatibility.
  • Kept the existing list conversion behavior after deserialization.
• System.Text.Json
  • Added a polymorphic resolver that registers dock interfaces and emits $type discriminators.
  • Filtered interface properties by name when their concrete implementations are marked IgnoreDataMember or use ICommand.
  • Enabled NumberHandling for named floating point literals.
• YAML
  • Added dynamic type resolution and tag mappings for all dock model types so interface collections can deserialize.
  • Filtered IgnoreDataMember and ICommand properties via a custom type inspector.
  • Ensured round-trip settings remain enabled.
• Protobuf
  • Built a per-serializer RuntimeTypeModel that registers dock interfaces and classes.
  • Explicitly registered DataMember properties (including inherited ones) in deterministic order.
  • Modeled interface hierarchies with stable subtype tags to support interface-typed properties and collections.
• Tests
  • Added a layout round-trip test that exercises Newtonsoft, System.Text.Json, YAML, XML, and Protobuf serializers.

Usage Guide

• All serializers continue to implement IDockSerializer and can be used interchangeably. Example:

using Dock.Model.Core;
using Dock.Serializer.SystemTextJson;

IDockSerializer serializer = new DockSerializer();
using var stream = File.Create("layout.json");
serializer.Save(stream, rootDock);

stream.Position = 0;
var loaded = serializer.Load<RootDock>(stream);

• System.Text.Json and YAML now embed concrete type information:
  • JSON uses a $type discriminator with the full type name.
  • YAML uses tags in the form !Namespace.TypeName.
• XML, YAML, and Protobuf discover concrete types at runtime. Ensure the model assemblies you need are loaded (for example by referencing the model library or touching a type) before deserializing layouts.
• For custom list types, continue to pass the list type into the serializer constructor, for example new DockYamlSerializer(typeof(List<>)).

Fixes #924