feat(linear-static-mitc4-shell): step 5 - mitc4-physical-recovery

include/fesa/elements/mitc4_shell.hpp

@@ -2,6 +2,7 @@
 
 #include "fesa/core/status.hpp"
 #include "fesa/math/matrix.hpp"
+#include "fesa/math/vector.hpp"
 #include "fesa/model/model_types.hpp"
 
 #include <array>
@@ -39,8 +40,21 @@ struct Mitc4Stiffness {
     double drillingStiffness;
 };
 
-// Concrete small-rotation MITC4 kinematics, constitutive, and stiffness kernel.
-// Global equation ownership, physical recovery, and assembly remain outside.
+struct Mitc4PhysicalRecoveryPoint {
+    std::array<double, 2> naturalCoordinates;
+    Mitc4LocalFrame localFrame;
+    std::array<double, 8> generalizedStrain;
+    std::array<double, 8> sectionResultant;
+    std::array<std::array<double, 3>, 3> inPlaneStress;
+};
+
+struct Mitc4PhysicalRecovery {
+    std::array<Mitc4PhysicalRecoveryPoint, 4> points;
+    double strainEnergy;
+};
+
+// Concrete small-rotation MITC4 kinematics, constitutive, stiffness, and
+// physical-only recovery kernel. Global equation/result ownership remains outside.
 class Mitc4Shell {
 public:
     static Result<Mitc4Shell> create(
@@ -73,6 +87,8 @@ public:
     [[nodiscard]] Matrix bendingSectionMatrix() const;
     [[nodiscard]] Matrix transverseShearSectionMatrix() const;
     [[nodiscard]] Result<Mitc4Stiffness> stiffness() const;
+    [[nodiscard]] Result<Mitc4PhysicalRecovery> recoverPhysical(
+        const Vector& globalElementDisplacement24) const;
 
 private:
     using Vector3 = std::array<double, 3>;