feat(newton): first newton solver implementation

experiments/preconditioning_diagnostics.cpp

@@ -218,7 +218,7 @@ TEST_CASE(
         integral::FixedTotalMass({.Mtotal = dimensions::MassValue{targetMass}}),
         constraint::FixedCentralDensity({.RhoC = dimensions::DensityValue{centralDensity}})
     );
-    auto problem                            = equilibrium::discretize(stellarModel, finiteElementModel);
+    auto problem                            = equilibrium::discretize(stellarModel, std::move(finiteElementModel));
     const double problemConstructionSeconds = maximum_rank_seconds(problemConstructionStart, communicator);
     announce(communicator, "P0 extended baseline: projecting the Lane-Emden seed");