Mini-rust in Rust 038: Avoiding a String allocation for each token

Last time I described what I tried to do with removing the extra String stored in each Token. This time, having figured out a workaround, we go ahead and remove them. Of course, it's more complicated than we expected. More info: https://artificialworlds.net/blog/2025/07/18/mini-rust-in-rust-038-no-strings-in-tokens