feat(thermal): assemble heat operators and preserve typed frame history

include/fesa/results/thermal_result_records.h

@@ -0,0 +1,53 @@
+#ifndef FESA_RESULTS_THERMAL_RESULT_RECORDS_H_
+#define FESA_RESULTS_THERMAL_RESULT_RECORDS_H_
+
+#include <array>
+#include <cstdint>
+#include <optional>
+#include <vector>
+
+#include "fesa/core/source_identity.h"
+#include "fesa/math/vector.h"
+#include "fesa/math/vector3.h"
+
+namespace fesa {
+
+/// @brief Identifies a prescribed temperature by Domain node and source DOF
+/// 11/15.
+struct ThermalReactionDof {
+  EntityIndex node;
+  int source_dof;
+};
+
+/// @brief Holds four CCW surface points times six ordered global flux traces.
+/// @note Row=6*point+trace; traces are -1+, -.5, 0-, 0+, .5, 1-.
+using ThermalElementFlux = std::array<Vector3, 24>;
+/// @brief Holds R columns e1,e2,n at each of four CCW surface points.
+using ThermalElementFrames = std::array<std::array<Vector3, 3>, 4>;
+
+/// @brief Holds recovery present only at completed increments, including P=0.
+struct ThermalCompletedPayload {
+  std::vector<ThermalReactionDof> reaction_dofs;
+  Vector reaction_heat_rate{0U};  // Power, positive into the model.
+  std::vector<EntityIndex> element_order;
+  std::vector<ThermalElementFlux> global_heat_flux;  // Power/area.
+};
+
+/// @brief Carries an initial or completed thermal frame with explicit row
+/// mapping.
+/// @note Source identities are resolved through the state's immutable
+/// inventory.
+struct ThermalAcceptedFrame {
+  std::uint64_t frame_index = 0U;
+  std::uint64_t increment_index = 0U;
+  double time = 0;
+  double time_increment = 0;
+  bool is_initial = true;
+  std::vector<EntityIndex> node_order;
+  Vector temperature{
+      0U};  // Node-major, source DOFs 11..15; signed temperature.
+  std::optional<ThermalCompletedPayload> completed;
+};
+
+}  // namespace fesa
+#endif  // FESA_RESULTS_THERMAL_RESULT_RECORDS_H_