feat: add thermal dof mapping

include/fesa/fem/dof_manager.h

@@ -9,12 +9,15 @@
 #include "fesa/analysis/analysis_model.h"
 #include "fesa/constraints/boundary_condition.h"
 #include "fesa/elements/element.h"
+#include "fesa/elements/thermal_element_layout.h"
 #include "fesa/math/vector.h"
 
 namespace fesa {
 
 class DofManagerTestAccess;
 
+enum class DofProfile { kStructural, kThermal };
+
 /// @brief Stores the stable structural CSR pattern.
 struct SparsePattern {
   std::vector<std::size_t> row_offsets;
@@ -32,6 +35,9 @@ class DofManager {
   /// the procedure-owned runtime element view supersedes it in Step 20.
   static Result<DofManager> Create(const AnalysisModel& model);
 
+  /// @brief Builds the active DS4 five-station equation mapping.
+  static Result<DofManager> CreateThermal(const AnalysisModel& model);
+
   /// @brief Builds mappings from runtime element layouts in supplied order.
   /// @param analysis_model Non-owning active model view that outlives this
   /// call.
@@ -46,6 +52,13 @@ class DofManager {
   Status Build(const AnalysisModel& analysis_model, const ElementView& elements,
                const BoundaryConditionView& boundaries);
 
+  /// @brief Builds thermal mappings from stable DS4 semantic layouts.
+  Status BuildThermal(const AnalysisModel& analysis_model,
+                      const std::vector<ThermalElementDofLayout>& layouts);
+
+  /// @brief Reports which physical component profile owns this mapping.
+  DofProfile Profile() const noexcept;
+
   /// @brief Returns the full node-by-component DOF count.
   std::size_t FullDofCount() const noexcept;
   /// @brief Returns the free-equation count.
@@ -54,12 +67,18 @@ class DofManager {
   std::size_t ConstrainedDofCount() const noexcept;
   /// @brief Maps a stable node index and component to a full DOF.
   std::size_t FullDof(EntityIndex node, DofComponent component) const;
+  /// @brief Maps an active thermal Domain node and station to a full DOF.
+  std::size_t FullThermalDof(EntityIndex node,
+                             ThermalDofComponent component) const;
   /// @brief Returns the free equation for a full DOF when unconstrained.
   std::optional<std::size_t> FreeEquation(std::size_t full_dof) const;
   /// @brief Maps one declared runtime layout to stable full DOFs.
   /// @return The declared node/component scatter or a layout failure.
   Result<std::vector<std::size_t>> ElementScatter(
       const ElementDofLayout& layout) const;
+  /// @brief Maps one DS4 layout to its node-major 20-entry scatter.
+  Result<std::vector<std::size_t>> ThermalElementScatter(
+      const ThermalElementDofLayout& layout) const;
   /// @brief Returns a beam scatter in endpoint/component order.
   /// @note This compatibility wrapper delegates to the generic stored layout.
   std::array<std::size_t, 12> ElementScatter(EntityIndex element) const;
@@ -100,6 +119,8 @@ class DofManager {
   std::vector<std::size_t> constrained_dofs_;
   Vector prescribed_values_{0U};
   SparsePattern sparse_pattern_;
+  DofProfile profile_{DofProfile::kStructural};
+  std::vector<std::optional<std::size_t>> thermal_node_rows_;
 };
 
 }  // namespace fesa