flake.nix: add devshell

.envrc

@@ -0,0 +1 @@
+use flake

.gitignore

@@ -0,0 +1,2 @@
+result
+result-*

flake.lock

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+{
+  "nodes": {
+    "nixpkgs": {
+      "locked": {
+        "lastModified": 1779877693,
+        "narHash": "sha256-NOF9NAREhxr50bbBfVcVOq+ArCMSoe8dP79Pk2uyARk=",
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "4100e830e085863741bc69b156ec4ccd53ab5be0",
+        "type": "github"
+      },
+      "original": {
+        "owner": "NixOS",
+        "ref": "nixpkgs-unstable",
+        "repo": "nixpkgs",
+        "type": "github"
+      }
+    },
+    "root": {
+      "inputs": {
+        "nixpkgs": "nixpkgs"
+      }
+    }
+  },
+  "root": "root",
+  "version": 7
+}

flake.nix

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+{
+  inputs.nixpkgs.url = "github:NixOS/nixpkgs/nixpkgs-unstable";
+
+  outputs = { self, nixpkgs }: let
+    inherit (nixpkgs) lib;
+
+    systems = [
+      "x86_64-linux"
+      "aarch64-linux"
+      "x86_64-darwin"
+      "aarch64-darwin"
+      "armv7l-linux"
+    ];
+
+    forAllSystems = f: lib.genAttrs systems (system: f system nixpkgs.legacyPackages.${system});
+  in {
+    devShells = forAllSystems (_: pkgs: {
+      default = pkgs.mkShell {
+        packages = with pkgs; [
+          python3
+          ruff
+        ];
+      };
+    });
+  };
+}