perf(allocations): reduced overall allocations by 95%, increaseed jacobian applicatin by 2x

This commit uses global pre allocated work space to dramatically reduce memory usage and allocation time

libmeanfield/interface/operators/prepared_variadic_stellar_equilibrium.cppm

@@ -2785,6 +2785,22 @@ export namespace mean_field::operators {
             return *m_physical;
         }
 
+        void BuildVolumeDisplacementDirection(
+            const mfem::Vector &stateDirection,
+            mfem::Vector &volumeDisplacementDirection
+        ) const {
+            if (stateDirection.Size() != Width()) {
+                throw std::invalid_argument(
+                    "The prepared stellar-equilibrium root received a state direction with the wrong size."
+                );
+            }
+            const auto rootDirection = m_manifest.directionView(stateDirection);
+            m_physical->BuildVolumeDisplacementDirection(
+                rootDirection.block(utils::blocks::surface_deformation_field.parameters_term),
+                volumeDisplacementDirection
+            );
+        }
+
         template <models::ModelSpecification Specification>
             requires ModelType::template
         containsSpecification<Specification> [[nodiscard]] const auto &GetPreparedContribution() const noexcept {