Fix venv being created with incorrect Python

.github/workflows/test.yml

@@ -100,8 +100,9 @@ jobs:
           allow-prereleases: true
 
       - uses: yezz123/setup-uv@ab6be5a42627f19dc36e57b548592a5e52cece4a # v4.1
-        with:
-          uv-venv: "venv"
+
+      - name: Set up virtual environment
+        run: uv venv --python 3.13t
 
       # 1. Test suite with free-threading enabled, but no free-threading-specific plugins
       - name: Run free-threaded tests on ${{ matrix.platform}}
@@ -118,12 +119,14 @@ jobs:
           UV_NO_CACHE: "true"
         run: |
           python3.13t -VV
+          source .venv/bin/activate
           uv pip install --upgrade --only-binary :all: numpy scipy
 
       - name: Run free-threaded tests with ${{ matrix.plugin }} on ${{ matrix.platform}}
         if: ${{ matrix.plugin != 'none' }}
         run: |
           python3.13t -VV
+          source .venv/bin/activate
           uv pip install -e .
           uv pip install pytest ${{ matrix.plugin }}
           if [ "${{ matrix.plugin }}" == "pytest-run-parallel" ]; then