Integrate Refactor solver sources and dual MSVC CMake builds

include/fesa/math/matrix.h

@@ -32,6 +32,26 @@ class Matrix {
   /// @brief Returns the column count.
   std::size_t Columns() const noexcept;
 
+  /// @brief Returns mutable row-major contiguous storage.
+  /// @note Borrows Rows()*Columns() entries until storage is moved, assigned
+  /// or destroyed.
+  double* Data() noexcept;
+
+  /// @brief Returns immutable row-major contiguous storage.
+  /// @note Borrows Rows()*Columns() entries until storage is moved, assigned
+  /// or destroyed.
+  const double* Data() const noexcept;
+
+  /// @brief Computes the robust Frobenius norm through the dense backend.
+  /// @note Empty storage has zero norm; nonfinite values propagate as in Vector.
+  /// @throws std::length_error if storage exceeds the backend integer range.
+  double Norm() const;
+
+  /// @brief Scales every entry by alpha through the dense backend.
+  /// @note Empty storage is unchanged; nonfinite values follow BLAS semantics.
+  /// @throws std::length_error if storage exceeds the backend integer range.
+  void Scale(double alpha);
+
   /// @brief Returns a bounds-checked mutable entry.
   /// @throws std::out_of_range if the index is outside the matrix.
   double& operator()(std::size_t row, std::size_t column);