ci: nix image for job

.gitea/workflows/nix-test.yaml

@@ -1,22 +1,21 @@
-name: Nix Test
+name: Nix Test (Isolated)
 on: [push]
 
 jobs:
   test-nix:
-    runs-on: ubuntu-latest
+    # Теперь используем наш новый лейбл nixos
+    runs-on: nixos
     steps:
       - name: Checkout repository
         uses: actions/checkout@v4
 
-      - name: Install Nix
-        uses: https://github.com/nixbuild/nix-quick-install-action@v30
-        with:
-          nix_conf: |
-            sandbox = false
-            experimental-features = nix-command flakes
-
       - name: Build with Nix
         run: |
-          nix build .#default
-          ./result/bin/hello
+          # Включаем flakes (в образе nixos/nix они могут быть не активны по умолчанию)
+          export NIX_CONFIG="experimental-features = nix-command flakes"
           
+          # Просто собираем
+          nix build .#default
+          
+          # Проверяем результат
+          ./result/bin/hello