Very strong engine. Well done.
My Ninny Chess Club follows a similar pattern -- UCI engine with personalities built on a PeSTO foundation, then converted to run as WASM. Have a look.
NNUE is an fascinating and throughly modern approach, just like your Rust choice. Ninny Chess Club doesn't need NNUE to crush human opponents, although I considered it. Instead, I went with standard classical chess engine techniques I remember from Shredder and Crafty days. PeSTO keeps it very fast, of course. Hope you give it a go on "Deadly" level vs. Prodigy. Good luck with GaiaChess.