When Kelsey Plum stepped away from her Under Armour partnership, it didn’t feel like an ending. The combination of the WNBA negotiating a new CBA, increased league attention, expanded media rights and Plum's sneaker-free-agency, it felt like a breath of fresh air. Moments like this tend to shine alight on a player’s memorabilia, especially with Panini as a key WNBA partner. If that sounds familiar, it should. Late last year, Stephen Curry entered his own version of sneaker free agency , rotating through wearing Kobes, Jordans, and deep cuts while the basketball world watched closely.  Now WNBA star and style icon Plum now finds herself in a similar position—and for collectors, that kind of moment often matters as much as performance.…