Root flake with two outputs: devShells.default (pinned 1.95.0
toolchain via rust-toolchain.toml + rust-overlay, plus cargo-sweep)
and packages.default (rustPlatform.buildRustPackage from the committed
Cargo.lock; doCheck=false). flake.lock pins nixpkgs nixos-26.05 /
rust-overlay / flake-utils. .envrc (use flake) for direnv parity.
Single source of toolchain for dev and the upcoming CI, so they can't
drift. Verified through the flake: nix build yields a working binary,
clippy clean, 2424 tests pass / 0 fail / 1 intentional ignored doctest.
First step toward requirements.md TT5 + D1/D2/D3.
claude@clouddev1