Snapshot optimized solver and audit diagnostics before numerical experiments

libmeanfield/interface/mapping/compactification/kelvin.cppm

@@ -34,6 +34,16 @@ export namespace mean_field::mapping::compactification {
         [[nodiscard]] double GetReferenceInfinityRadius() const noexcept;
         [[nodiscard]] double GetCoordinateTolerance() const noexcept;
 
+        // Factors in delta J = scale * grad(delta u) + delta u (grad scale)^T.
+        // They depend only on the fixed compactification coordinate, so prepared
+        // operators can compute them once instead of evaluating the full map.
+        [[nodiscard]] MappingStatus EvaluateJacobianVariationFactors(
+            double coordinate,
+            const mfem::Vector &coordinateGradient,
+            double &scale,
+            mfem::Vector &scaleGradient
+        ) const;
+
     private:
         struct RadialFactors {
             double coordinate;