fix(math): preflight finite dense operands at dispatch boundary

src/fesa/math/dense_blas_internal.h

@@ -31,7 +31,7 @@ class ScopedSingleEquationThreads {
 Result<MKL_INT> ToMklSize(std::size_t size);
 
 /// @brief Computes left-transpose times right through ordinary dense MKL.
-/// @throws std::invalid_argument if the row counts differ.
+/// @throws std::invalid_argument for mismatched rows or nonfinite operands.
 Matrix MultiplyTransposeLeft(const Matrix& left, const Matrix& right);
 
 /// @brief Multiplies a compact diagonal matrix by a vector through MKL.