fix: add virtual environment creation and activation to GitHub Actions workflow

Author: kirill-markin

.github/workflows/tests.yml

@@ -19,10 +19,13 @@ jobs:
         curl -LsSf https://astral.sh/uv/install.sh | sh
         echo "$HOME/.cargo/bin" >> $GITHUB_PATH
         
-    - name: Install dependencies
+    - name: Create virtual environment and install dependencies
       run: |
+        uv venv
+        . .venv/bin/activate
         uv pip install -e ".[dev]"
         
     - name: Run tests
       run: |
+        . .venv/bin/activate
         uv run pytest tests/ -v