M6.13: Sex picker + species variant schema

Adds character Sex (male/female) as a top-level CharacterDraft field
required for every character, and species variants as a layer on top
of the base species record. Two variant axes:

  - "sex": auto-resolves from CharacterDraft.Sex for purebreds; for
           hybrids, pinned by parent role (sire = male, dam = female)
           by definition. No picker needed beyond Step 0.
  - "lineage": explicit per-species pick (Ram-Folk's sheep/goat). Has
               its own picker on Step 1 (purebred path under the grid;
               hybrid path embedded into the per-parent pick column).

Schema (Theriapolis.Core/Data):
  - SpeciesDef gains VariantAxis (string) and Variants (array of
    SpeciesVariantDef { Id, Name, Traits, Detriments }).
  - JSON content not yet populated — that's M6.14.

CharacterDraft adds:
  - Sex (required by Step 0 validation)
  - SpeciesVariant / SireSpeciesVariant / DamSpeciesVariant
  - ResolveVariantId(species, role) that returns the active variant
    id for a given context — used by Aside to layer variant traits
    onto the base species traits.

Step 0 (StepClade): sex picker row above the hybrid toggle. Two
toggle buttons radio-style.

Step 1 (StepSpecies): purebred path renders a lineage picker below
the grid when the picked species has VariantAxis == "lineage";
hybrid path embeds a lineage picker at the top of each parent's
pick column. Hover popovers summarise each variant's contents.

Validation: Sex is required at Step 0. Lineage variant required at
Step 1 for any picked species (purebred or per-hybrid-parent) with
VariantAxis == "lineage".

Aside: AddVariantContent layers the resolved variant's extra
traits/detriments onto the base species rendering, for both purebred
and hybrid paths.

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

Theriapolis.Godot/UI/CharacterDraft.cs

@@ -28,6 +28,23 @@ public partial class CharacterDraft : Resource
     [Export] public string SubclassId   { get; set; } = "";
     [Export] public string BackgroundId { get; set; } = "";
 
+    /// <summary>"male" or "female". Required for every character. For
+    /// purebreds with sex-axis variants (Elk, Lion), drives variant
+    /// resolution. For hybrids, sire variant always resolves to "male"
+    /// and dam variant to "female" by parent-role definition — the
+    /// character's own Sex remains an identity field.</summary>
+    [Export] public string Sex { get; set; } = "";
+
+    /// <summary>Lineage-axis variant id picked for the purebred species
+    /// (e.g. "sheep" or "goat" for Ram-Folk). Empty if the picked species
+    /// has no lineage variant.</summary>
+    [Export] public string SpeciesVariant { get; set; } = "";
+
+    /// <summary>Hybrid: lineage-axis variant for sire's species.</summary>
+    [Export] public string SireSpeciesVariant { get; set; } = "";
+    /// <summary>Hybrid: lineage-axis variant for dam's species.</summary>
+    [Export] public string DamSpeciesVariant  { get; set; } = "";
+
     // ── Phase 6.5 hybrid origin ────────────────────────────────────────
     /// <summary>True when the PC is a hybrid (two parent lineages).</summary>
     [Export] public bool IsHybrid { get; set; }
@@ -67,6 +84,36 @@ public partial class CharacterDraft : Resource
     public int CladeTraitLimit(string lineage) =>
         lineage == DominantParent ? 2 : 1;
 
+    /// <summary>
+    /// Resolves the active variant id for a species. <paramref name="role"/>
+    /// is "" for purebred, "sire" or "dam" for hybrid lineages. Returns
+    /// empty when the species has no variants or the relevant pick/sex is
+    /// missing.
+    /// </summary>
+    public string ResolveVariantId(Theriapolis.Core.Data.SpeciesDef? species, string role)
+    {
+        if (species is null || string.IsNullOrEmpty(species.VariantAxis)) return "";
+        return species.VariantAxis switch
+        {
+            // Sex-axis: purebred uses character Sex; hybrid lineages are
+            // pinned by parent role (sire = male, dam = female).
+            "sex" => role switch
+            {
+                "sire" => "male",
+                "dam"  => "female",
+                _      => Sex,
+            },
+            // Lineage-axis: explicit per-species pick.
+            "lineage" => role switch
+            {
+                "sire" => SireSpeciesVariant,
+                "dam"  => DamSpeciesVariant,
+                _      => SpeciesVariant,
+            },
+            _ => "",
+        };
+    }
+
     /// <summary>
     /// Resolves the "active" clade for downstream steps (Class / Subclass
     /// / Background). Purebred uses <see cref="CladeId"/>; hybrids use
@@ -149,6 +196,10 @@ public partial class CharacterDraft : Resource
                 case "dam_chosen_species_trait":     DamChosenSpeciesTrait = (string)patch[key]; break;
                 case "sire_chosen_species_detriment":SireChosenSpeciesDetriment = (string)patch[key]; break;
                 case "dam_chosen_species_detriment": DamChosenSpeciesDetriment = (string)patch[key]; break;
+                case "sex":                     Sex = (string)patch[key]; break;
+                case "species_variant":         SpeciesVariant = (string)patch[key]; break;
+                case "sire_species_variant":    SireSpeciesVariant = (string)patch[key]; break;
+                case "dam_species_variant":     DamSpeciesVariant = (string)patch[key]; break;
                 default:
                     GD.PushWarning($"[CharacterDraft] unknown patch key: {k}");
                     break;