add missing nixops4 package

panel/nix/configuration.nix

@@ -2,6 +2,7 @@
   config,
   pkgs,
   lib,
+  inputs,
   ...
 }:
 let
@@ -145,6 +146,19 @@ in
         NixOps4 from the package's npins-based code, we will have to do with
         this workaround.
       '';
+      default =
+        let
+          sources = import ../../npins;
+          inherit (import sources.flake-inputs) import-flake load-flake;
+          inherit
+            (import-flake {
+              src = ../../.;
+            })
+            inputs
+            ;
+          inherit (inputs) nixops4;
+        in
+        (load-flake nixops4).packages.${pkgs.system}.default;
     };
 
     deployment = {