Implementar figura ICOSAHEDRON (D20 poliedro) - Tecla U

- Nueva clase IcosahedronShape con 12 vértices golden ratio
- Vértices basados en 3 rectángulos áureos ortogonales
- Subdivisión de caras para más de 12 puntos
- Rotación triple simultánea (X, Y, Z)
- Proyección a esfera circunscrita
- Compatible con física spring-damper y z-sorting

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

source/engine.cpp

@@ -23,12 +23,13 @@
 #include "ball.h"              // for Ball
 #include "external/dbgtxt.h"   // for dbg_init, dbg_print
 #include "external/texture.h"  // for Texture
-#include "shapes/sphere_shape.h"     // for SphereShape
-#include "shapes/cube_shape.h"       // for CubeShape
-#include "shapes/helix_shape.h"      // for HelixShape
-#include "shapes/wave_grid_shape.h"  // for WaveGridShape
-#include "shapes/torus_shape.h"      // for TorusShape
-#include "shapes/cylinder_shape.h"   // for CylinderShape
+#include "shapes/sphere_shape.h"        // for SphereShape
+#include "shapes/cube_shape.h"          // for CubeShape
+#include "shapes/helix_shape.h"         // for HelixShape
+#include "shapes/wave_grid_shape.h"     // for WaveGridShape
+#include "shapes/torus_shape.h"         // for TorusShape
+#include "shapes/cylinder_shape.h"      // for CylinderShape
+#include "shapes/icosahedron_shape.h"   // for IcosahedronShape
 
 // Función auxiliar para obtener la ruta del directorio del ejecutable
 std::string getExecutableDirectory() {
@@ -1084,6 +1085,9 @@ void Engine::activateShape(ShapeType type) {
         case ShapeType::CYLINDER:
             active_shape_ = std::make_unique<CylinderShape>();
             break;
+        case ShapeType::ICOSAHEDRON:
+            active_shape_ = std::make_unique<IcosahedronShape>();
+            break;
         // Futuras figuras se añadirán aquí
         default:
             active_shape_ = std::make_unique<SphereShape>();  // Fallback