ci: add GitHub Actions CI pipeline

Runs pytest on push/PR to master.

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

Author: dbhavery

.github/workflows/ci.yml

@@ -0,0 +1,20 @@
+name: CI
+
+on:
+  push:
+    branches: [master]
+  pull_request:
+    branches: [master]
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-python@v5
+        with:
+          python-version: "3.13"
+      - name: Install package
+        run: pip install -e ".[dev]"
+      - name: Run tests
+        run: pytest --tb=short -q