feat(thermal): add local shell kernel and time grid

src/fesa/elements/thermal_shell_geometry.h

@@ -0,0 +1,10 @@
+#ifndef FESA_ELEMENTS_THERMAL_SHELL_GEOMETRY_H_
+#define FESA_ELEMENTS_THERMAL_SHELL_GEOMETRY_H_
+#include <array>
+#include "fesa/core/status.h"
+#include "fesa/math/vector3.h"
+namespace fesa {
+/// @brief Validates the finite, oriented Q4 geometry used by the thermal kernel.
+Status ValidateThermalShellGeometry(const std::array<Vector3,4>& coordinates);
+}
+#endif