feat: adopt lumped mass and reduced-coordinate shell HHT

Integrate Hex8 mass verification and fixed-null-basis shell dynamics with numerical and physics handoff evidence. Preserve interrupted reference and full-validation status; full integration validation is deferred until after performance optimization.

src/fesa/analysis/solid_hht_dynamic_procedure.cpp

@@ -119,7 +119,7 @@ void AppendMatrix(const Matrix& local, const RuntimeSolid& solid, std::size_t e,
       coo->push_back(
           {solid.scatter[i], solid.scatter[j], local(i, j), e, 24 * i + j});
 }
-/// @brief Assembles constant reference consistent mass once without lumping.
+/// @brief Assembles constant reference row-sum lumped mass once.
 Result<SparseMatrix> AssembleMass(const std::vector<RuntimeSolid>& solids,
                                   const DofManager& dofs) {
   std::vector<CooContribution> coo;