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/Wizard.cs

@@ -51,7 +51,7 @@ public partial class Wizard : Control
         typeof(Steps.StepBackground),  // 4 History
         typeof(Steps.StepStats),       // 5 Abilities
         typeof(Steps.StepSkills),      // 6 Skills
-        null,                           // 7 Sign      — M6.6
+        typeof(Steps.StepReview),      // 7 Sign
     };
 
     public override void _Ready()