fix: conditional optional deps install for Python 3.13 CI

On 3.13, astropy fails to build from source due to removed
setuptools.dep_util. Install [optional] extras only on 3.12.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: 2 people

.github/workflows/main.yml

@@ -60,7 +60,10 @@ jobs:
         pip3 install setuptools
         pip3 install wheel
         pip3 install pytest coverage pytest-cov
-        pip install ./PyAutoConf "./PyAutoFit[optional]"
+        pip install ./PyAutoConf ./PyAutoFit
+        if [ "${{ matrix.python-version }}" = "3.12" ]; then
+          pip install "./PyAutoFit[optional]"
+        fi
     - name: Run tests
       run: |
         export ROOT_DIR=`pwd`