Move hydra-spec to input repository (#1512)

Moves the hydra-spec.pdf to
https://github.com/cardano-scaling/hydra-formal-specification

.github/workflows/ci-nix.yaml

@@ -276,14 +276,14 @@ jobs:
 
     - name: ❄ Build specification PDF
       run: |
-        nix build .#spec && cp result/*.pdf spec/
+        nix build .#spec && cp result/*.pdf .
 
     - name: 💾 Upload specification
       uses: actions/upload-artifact@v4
       with:
         name: hydra-spec
         path: |
-          ./spec/*.pdf
+          *.pdf
 
   documentation:
     name: Documentation

flake.nix

@@ -21,6 +21,7 @@
     cardano-node.url = "github:intersectmbo/cardano-node/9.1.0";
     mithril.url = "github:input-output-hk/mithril/2428.0";
     nix-npm-buildpackage.url = "github:serokell/nix-npm-buildpackage";
+    hydra-spec.url = "github:cardano-scaling/hydra-formal-specification";
   };
 
   outputs =
@@ -130,9 +131,7 @@
           packages =
             hydraPackages //
             (if pkgs.stdenv.isLinux then (prefixAttrs "docker-" hydraImages) else { }) // {
-              spec = import ./spec {
-                inherit pkgs;
-              };
+              spec = inputs.hydra-spec.packages.${system}.default;
             };
           process-compose."demo" = import ./nix/hydra/demo.nix {
             inherit system pkgs inputs self;