Reorganize firefox-tabs script into subfolder with flake.nix and plan.md

scripts/firefox-tabs/flake.nix

@@ -0,0 +1,30 @@
+{
+  description = "Firefox tabs script environment";
+
+  inputs = {
+    nixpkgs.url = "github:NixOS/nixpkgs/nixpkgs-unstable";
+  };
+
+  outputs = { self, nixpkgs }:
+    let
+      system = "aarch64-darwin";
+      pkgs = import nixpkgs { inherit system; };
+      pythonEnv = pkgs.python3.withPackages (ps: with ps; [
+        lz4
+      ]);
+    in
+    {
+      devShells.${system}.default = pkgs.mkShell {
+        buildInputs = [
+          pythonEnv
+          pkgs.lz4
+        ];
+        shellHook = ''
+          echo "Firefox tabs script environment ready"
+          echo "Python: $(which python3)"
+          echo "Run: python3 firefox-tabs.py"
+        '';
+      };
+    };
+}
+