Prune commentary and stale Rust port notes

rust-toolchain.toml

@@ -1,11 +1,4 @@
-# iris needs nightly (see the #![feature] list in core/src/lib.rs and src/lib.rs).
-# The pin is dated rather than "nightly" because the const-traits feature set
-# changes shape between nightlies: on 2026-09-04 the vendored January tree would
-# not parse at all, because `impl const Trait for T` had become
-# `const impl Trait for T`. A rolling channel turns that into a build that
-# breaks unattended on whatever machine Dev Updater happens to build on.
-# Advance this deliberately, with the feature list in RUST.md's I0b.
 [toolchain]
-channel = "nightly-2026-09-03"
+channel = "nightly"
 components = ["clippy", "rustfmt"]
 targets = ["aarch64-linux-android", "x86_64-linux-android"]