ci: add go mod tidy & gomod2nix check CI

Signed-off-by: Seongmin Lee <[e-mail]>

.tangled/workflows/test.yml

···
     command: |
       mkdir -p appview/pages/static; touch appview/pages/static/x
 
+  - name: run go mod tidy
+    command: go mod tidy
+
+  - name: run gomod2nix
+    command: |
+      nix run .#gomod2nix
+
+  - name: verify no changes
+    command: |
+      if ! git diff --quiet; then
+        echo "Error: gomod2nix produced changes. Please commit the updated files."
+        git diff
+        exit 1
+      fi
+
   - name: run linter
     environment:
       CGO_ENABLED: 1

flake.nix

···
       gomod2nix = {
         type = "app";
         program = toString (pkgs.writeShellScript "gomod2nix" ''
+          HOME=$(mktemp -d)
+          echo $HOME
           ${gomod2nix.legacyPackages.${system}.gomod2nix}/bin/gomod2nix generate --outdir ./nix
         '');
       };