chore(packaging): Guix-only — remove flake.nix, add a real guix.scm

guix.scm

@@ -0,0 +1,53 @@
+;; SPDX-License-Identifier: MPL-2.0
+;; SPDX-FileCopyrightText: 2026 Jonathan D.A. Jewell <j.d.a.jewell@open.ac.uk>
+;;
+;; Guix development manifest for VeriSimDB.
+;;
+;;     guix shell -m guix.scm
+;;
+;; SCOPE — read this before extending the file.
+;;
+;; This is a *development environment* manifest, not a package definition. It
+;; replaces the `flake.nix` dev shell removed in the same change, one-for-one:
+;; that file declared a toolchain, not a build, and said so in its own header.
+;; Nothing that existed before is lost by this swap.
+;;
+;; It is deliberately NOT a `(package ...)` with `cargo-build-system`. VeriSimDB
+;; is a 17-crate Rust workspace plus an Elixir/OTP layer; a correct
+;; `#:cargo-inputs` enumeration would need every transitive crate pinned, and a
+;; definition that merely *looks* like a package build while failing to produce
+;; one would be worse than this honest manifest — the estate already has enough
+;; artefacts that satisfy a presence check without doing anything. Promote this
+;; to a real package definition when someone can build and verify it end to end.
+;;
+;; NOT VALIDATED LOCALLY: Guix is not installed on the authoring machine, so
+;; this file has not been evaluated. Run `guix shell -m guix.scm -- true` before
+;; relying on it, and fix rather than delete it if a specification name has
+;; drifted.
+;;
+;; Toolchain rationale — each entry maps to something this repo actually uses:
+;;
+;;   rust, rust:cargo   17-crate workspace under rust-core/ (Cargo.toml)
+;;   rust:rustfmt       `cargo fmt` is enforced in CI
+;;   elixir, erlang     elixir-orchestration/ (mix, 647 tests)
+;;   coq                formal/ — 9 modules, gated by coq-build.yml
+;;   just               formal/Justfile and the root justfile
+;;   reuse              REUSE compliance is a required check (776/776)
+;;   git, gnu-make      assumed by several recipes
+;;
+;; Deliberately absent: Node, npm, Deno and friends. This repo's own
+;; NPM/Bun Blocker and TypeScript/JavaScript Blocker workflows reject them, and
+;; a template-supplied toolchain that installed them is exactly the class of
+;; drift those gates exist to catch.
+
+(specifications->manifest
+ (list "rust"
+       "rust:cargo"
+       "rust:rustfmt"
+       "elixir"
+       "erlang"
+       "coq"
+       "just"
+       "reuse"
+       "git"
+       "gnu-make"))