fix sdist CI; install python during workflow

.github/workflows/build-and-deploy.yml

@@ -31,6 +31,12 @@ jobs:
     steps:
     - uses: actions/checkout@v4
 
+    - name: Set up Python
+      uses: actions/setup-python@v5
+      with:
+        python-version: '3.12'
+        cache: pip
+
     - name: Build sdist
       run: pipx run build --sdist