Update validate workflow to use Nix development shell

Co-authored-by: ncrmro <8276365+ncrmro@users.noreply.github.com>

Author: Copilot

.github/workflows/validate.yml

@@ -18,23 +18,21 @@ jobs:
     steps:
       - uses: actions/checkout@v4
 
-      - name: Install uv
-        uses: astral-sh/setup-uv@v4
+      - name: Install Nix
+        uses: cachix/install-nix-action@v31
         with:
-          version: "latest"
+          nix_path: nixpkgs=channel:nixos-unstable
 
-      - name: Set up Python
-        uses: actions/setup-python@v5
-        with:
-          python-version: "3.11"
+      - name: Setup Nix development environment
+        uses: nicknovitski/nix-develop@v1
 
-      - name: Install dependencies
+      - name: Install Python dependencies
         run: uv sync --extra dev
 
       - name: Check formatting (ruff)
         run: |
-          uv run ruff format --check src/ tests/
-          uv run ruff check src/ tests/
+          ruff format --check src/ tests/
+          ruff check src/ tests/
 
       - name: Run tests
-        run: uv run pytest tests/ -v
+        run: pytest tests/ -v