`.envrc` runs `use flake` when Nix is present, so on the NixOS hosts
(programs.direnv.enable brings direnv and nix-direnv) cd'ing into a
clone gives the pinned Rust toolchain, clippy, rustfmt, cargo-deny and
make; on titan, which has no Nix, it does nothing. nix-direnv's cache,
.direnv/, is ignored. Checked on straylight in a throwaway copy:
cargo 1.95.0, cargo-deny 0.19.6, rustc from the Nix store.
Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
