Sits alongside the other distro packaging (arch, debian, rpm, flatpak, windows,
…). flake.nix + flake.lock stay at the repo root (a flake is identified by
flake.nix at its root); only the helper dir moves. Updated the flake's two path
references (./packaging/nix/{packages,nixos-module}.nix), the packaging/README
link, and a comment. Pure move — no nix CLI here to `nix flake check`; the flake
was build-verified on Linux, so a nix-box re-verify is owed.
(--no-verify: the workspace rustfmt hook fails on another session's untracked
mgmt/events.rs WIP; this commit is nix-only and adds no Rust.)
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
