ci: use isolated uv virtualenv for running tests in GitHub Actions

Author: Aadi Jain

.github/workflows/python-app.yml

@@ -33,11 +33,14 @@ jobs:
         python-version: "3.11"
     - name: Set up uv
       uses: astral-sh/setup-uv@v5
-    - name: Install lightweight test dependencies
-      run: |
-        uv pip install --system pytest polars numpy scipy scikit-learn pyyaml duckdb spacy
-        uv pip install --system https://github.com/explosion/spacy-models/releases/download/en_core_web_sm-3.8.0/en_core_web_sm-3.8.0-py3-none-any.whl
+      with:
+        enable-cache: true
     - name: Run Tests
       run: |
+        uv venv
+        source .venv/bin/activate
+        uv pip install pytest polars numpy scipy scikit-learn pyyaml duckdb spacy
+        uv pip install https://github.com/explosion/spacy-models/releases/download/en_core_web_sm-3.8.0/en_core_web_sm-3.8.0-py3-none-any.whl
         python -m pytest tests/ -v --ignore=tests/test_audio_utils.py
 
+