Initial commit: Theriapolis baseline at port/godot branch point

Captures the pre-Godot-port state of the codebase. This is the rollback
anchor for the Godot port (M0 of theriapolis-rpg-implementation-plan-godot-port.md).
All Phase 0 through Phase 6.5 work is included; Phase 7 is in flight.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Theriapolis.Core/Data/TraitDef.cs

@@ -0,0 +1,21 @@
+using System.Text.Json.Serialization;
+
+namespace Theriapolis.Core.Data;
+
+/// <summary>
+/// Trait or detriment entry shared by clades, species, and class features.
+/// Phase 5 mostly stores these as descriptive text — only a handful have
+/// real runtime mechanics (level-1 combat-touching features). The rest
+/// surface as flavor in tooltips and the character sheet UI.
+/// </summary>
+public sealed record TraitDef
+{
+    [JsonPropertyName("id")]
+    public string Id { get; init; } = "";
+
+    [JsonPropertyName("name")]
+    public string Name { get; init; } = "";
+
+    [JsonPropertyName("description")]
+    public string Description { get; init; } = "";
+}