The Collins–Dykema–Torres-Ayala positivity conjecture for symmetric matrices

Let $A$ and $B$ be symmetric matrices of the same size. For integers $m$ and $r$ with $m\geq r$ and both $m$ and $r$ even, consider the coefficient of $t^r$ in

$$\mathsf{trace}((A+tB)^m).$$

Collins–Dykema–Torres-Ayala conjecture. This coefficient is non-negative.

This question is a symmetric-matrix variant of the BMV positivity question. It was proved by Stahl and later simplified by Eremenko, so the conjecture is solved.