v0.4.2

flake.nix declares aarch64-darwin again, alongside x86_64-linux. Everything
else is a routine dependency bump and the documentation catching up with it.

Changed

• systems is [ "x86_64-linux" "aarch64-darwin" ] again. The
  2026-08-01 revision of the org package standard had dropped
  aarch64-darwin, on the grounds that a declared platform with no CI gate
  behind it is a claim nothing backs. That reasoning was reverted the next
  day: mkPackageFlake generates packages, checks, apps, and
  devShells from this one list, so dropping aarch64-darwin did not just
  remove an unverified package — it took nix build and nix develop off
  the development machine entirely. aarch64-darwin still carries no CI
  gate, and the standard now accepts that explicitly rather than pretending
  the list means "verified".
• nixpkgs and treefmt-nix bumped via nix flake update.

Documented

• Platform coverage
  and the README's development section described one declared system; both
  now state the two-system list, why it changed twice in three days, and why
  CI still evaluates and builds x86_64-linux alone (--all-systems would
  fail on a platform mismatch on ubuntu-latest, not widen coverage).
• The flake input pin shown in the README, Getting started, and the release
  process page moved from v0.4.1 to v0.4.2.