Add flake checks

Signed-off-by: Nikolaos Karaolidis <nick@karaolidis.com>

flake.lock

@@ -2,11 +2,11 @@
   "nodes": {
     "nixpkgs": {
       "locked": {
-        "lastModified": 1758427187,
-        "narHash": "sha256-pHpxZ/IyCwoTQPtFIAG2QaxuSm8jWzrzBGjwQZIttJc=",
+        "lastModified": 1754725699,
+        "narHash": "sha256-iAcj9T/Y+3DBy2J0N+yF9XQQQ8IEb5swLFzs23CdP88=",
         "owner": "NixOS",
         "repo": "nixpkgs",
-        "rev": "554be6495561ff07b6c724047bdd7e0716aa7b46",
+        "rev": "85dbfc7aaf52ecb755f87e577ddbe6dbbdbc1054",
         "type": "github"
       },
       "original": {
@@ -29,11 +29,11 @@
         ]
       },
       "locked": {
-        "lastModified": 1758206697,
-        "narHash": "sha256-/DbPkh6PZOgfueCbs3uzlk4ASU2nPPsiVWhpMCNkAd0=",
+        "lastModified": 1754847726,
+        "narHash": "sha256-2vX8QjO5lRsDbNYvN9hVHXLU6oMl+V/PsmIiJREG4rE=",
         "owner": "numtide",
         "repo": "treefmt-nix",
-        "rev": "128222dc911b8e2e18939537bed1762b7f3a04aa",
+        "rev": "7d81f6fb2e19bf84f1c65135d1060d829fae2408",
         "type": "github"
       },
       "original": {

flake.nix

@@ -29,15 +29,10 @@
         packages.${system} = import ./packages { inherit pkgs; };
         formatter.${system} = treefmt.config.build.wrapper;
 
-        checks.${system} =
-          let
-            packages = pkgs.lib.mapAttrs' (
-              n: pkgs.lib.nameValuePair "package-${n}"
-            ) inputs.self.packages.${system};
-
-            formatter.formatting = treefmt.config.build.check inputs.self;
-          in
-          packages // formatter;
+        checks.${system} = with inputs.self; {
+          packages = packages.${system};
+          formatter = treefmt.config.build.check inputs.self;
+        };
       }
     );
 }