PSSA: A non-transformer language model written from scratch in Rust

PSSA, a plastic state-space architecture, is a non-transformer language model written in Rust. It demonstrates superior performance compared to transformers on a held-out slice of 198,939 unseen tokens, achieving a cross-entropy of 3.997 versus 4.429, a perplexity of 54.4 versus 83.8, and a next-token accuracy of 24.1% versus 18.0%. This indicates better generalization rather than harder memorization. Contributions are welcome, particularly for kernel performance and recurrent baselines.