Integrate Refactor solver sources and dual MSVC CMake builds

include/fesa/analysis/linear_frequency_procedure.h

@@ -6,13 +6,23 @@
 namespace fesa {
 
 class Domain;
+class EigenSolver;
 
 /// @brief Executes the supported linear MITC4 frequency procedure.
 class LinearFrequencyProcedureExecutor final {
  public:
+  /// @brief Preserves default FEAST construction for existing callers.
+  LinearFrequencyProcedureExecutor() = default;
+
+  /// @brief Borrows a solver that must outlive this executor and its calls.
+  explicit LinearFrequencyProcedureExecutor(const EigenSolver& solver) : solver_(&solver) {}
+
   /// @brief Builds, solves, and validates one frequency modal candidate.
   /// @return Requested physical modes plus all-c validation evidence.
   Result<EigenAnalysisState> Execute(const Domain& domain) const;
+
+ private:
+  const EigenSolver* solver_{nullptr};
 };
 
 }  // namespace fesa