M6.6: StepReview signing + hybrid math revision

- New Step VIII (Review): name input and Confirm button that
  saves the finalized character to user://character.tres.
- Hybrid lineage rules simplified per project decision: drop
  the "no-stack on overlap, take +1 free elsewhere" rule from
  theriapolis-rpg-clades.md. Hybrids now pick one ability mod
  from each parent clade and they sum if they overlap.
  Removes HybridFreeAbility, the free-bonus picker row, and the
  overlap special case from AbilityCalc + WizardValidation.
- StepClade bonus rows now mutate in place (sync ButtonPressed)
  instead of tearing down on every Refresh — the old path freed
  the very button mid-Pressed-signal, leaving stale buttons next
  to the new ones.
- StepSkills drops the redundant "Calling: X · History: Y" meta
  line; both are already shown in the Aside summary.
- Aside hybrid section adds dual-species traits and the
  universal-hybrid detriment pills.

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

Theriapolis.Godot/Scenes/Steps/StepSkills.cs

@@ -23,7 +23,6 @@ public partial class StepSkills : VBoxContainer, IStep
 {
     private CharacterDraft _draft = null!;
     private Label _countLabel = null!;
-    private Label _classBgLabel = null!;
     private GridContainer _groupsGrid = null!;
 
     public void Bind(CharacterDraft draft)
@@ -52,15 +51,8 @@ public partial class StepSkills : VBoxContainer, IStep
             AutowrapMode = TextServer.AutowrapMode.WordSmart,
         });
 
-        var meta = new HBoxContainer();
-        meta.AddThemeConstantOverride("separation", 24);
-        AddChild(meta);
         _countLabel = new Label { Text = "0 / 0 chosen" };
-        meta.AddChild(_countLabel);
-        var spacer = new Control { SizeFlagsHorizontal = SizeFlags.ExpandFill };
-        meta.AddChild(spacer);
-        _classBgLabel = new Label { Text = "" };
-        meta.AddChild(_classBgLabel);
+        AddChild(_countLabel);
 
         _groupsGrid = new GridContainer
         {
@@ -86,9 +78,9 @@ public partial class StepSkills : VBoxContainer, IStep
         var classOptions = new HashSet<string>(cls?.SkillOptions ?? System.Array.Empty<string>());
         var chosen = new HashSet<string>(_draft.ChosenSkills);
 
-        _countLabel.Text = $"{chosen.Count} / {required} chosen   +{lockedFromBg.Count} sealed by background";
-        _classBgLabel.Text = (cls is null ? "Pick a calling first." :
-            $"Calling: {cls.Name}   ·   History: {bg?.Name ?? "—"}").ToUpperInvariant();
+        _countLabel.Text = cls is null
+            ? "Pick a calling first."
+            : $"{chosen.Count} / {required} chosen   +{lockedFromBg.Count} sealed by background";
 
         foreach (var c in _groupsGrid.GetChildren()) c.QueueFree();