Add pytest CI job to GitHub Actions workflow

- New 'test' job runs pytest on every push and PR
- 'deploy' job now requires 'test' to pass and only runs on main

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

Author: mathieuboudreau

.github/workflows/deploy.yml

@@ -4,6 +4,7 @@ on:
   push:
     branches:
       - main
+  pull_request:
 
 env:
   # BASE_URL sets the path the site is served from (repo name for GitHub Pages)
@@ -21,7 +22,25 @@ concurrency:
   cancel-in-progress: false
 
 jobs:
+  test:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Setup Python
+        uses: actions/setup-python@v5
+        with:
+          python-version: '3.11'
+
+      - name: Install Python dependencies
+        run: pip install -r requirements.txt
+
+      - name: Run tests
+        run: pytest tests/ -v
+
   deploy:
+    needs: test
+    if: github.ref == 'refs/heads/main'
     environment:
       name: github-pages
       url: ${{ steps.deployment.outputs.page_url }}