feat(hex8): preserve full high-low state in dynamic element responses

tests/CMakeLists.txt

@@ -38,6 +38,7 @@ add_executable(
     unit/core/status_test.cpp
     unit/elements/element_factory_test.cpp
     unit/elements/hex8_element_test.cpp
+    unit/elements/hex8_high_low_test.cpp
     unit/elements/euler_beam_3d_test.cpp
     unit/elements/finite_rotation_test.cpp
     unit/elements/mitc4_shell_test.cpp
@@ -48,6 +49,7 @@ add_executable(
     unit/elements/thermal_shell_test.cpp
     unit/fem/dof_manager_test.cpp
     unit/math/dense_blas_internal_test.cpp
+    unit/math/high_low_arithmetic_test.cpp
     unit/math/matrix_test.cpp
     unit/math/sparse_matrix_test.cpp
     unit/math/vector3_test.cpp