fix: add missing package installation in publish workflow

- Add 'pip install -e .' to install solarwindpy before running tests
- Resolves all 45 test import errors: ModuleNotFoundError: No module named 'solarwindpy'
- Aligns with working ci.yml workflow pattern
- Enables proper test validation before PyPI deployment

Root cause: publish.yml workflow never installed the package being tested
Impact: CI/CD pipeline has been broken since inception - no tests were running

Author: blalterman

.github/workflows/publish.yml

@@ -63,6 +63,7 @@ jobs:
           python -m pip install --upgrade pip
           pip install build twine
           pip install -r requirements-dev.txt
+          pip install -e .  # Install solarwindpy package for testing
       
       - name: Run full test suite
         run: |