ci: add GitHub Actions workflow for lint, type check, and tests

Run ruff, mypy, bandit, and pytest across Python 3.9-3.13.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: stanwu

.github/workflows/ci.yml

@@ -0,0 +1,40 @@
+name: CI
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+    branches: [main]
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        python-version: ["3.9", "3.10", "3.11", "3.12", "3.13"]
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Set up Python ${{ matrix.python-version }}
+        uses: actions/setup-python@v5
+        with:
+          python-version: ${{ matrix.python-version }}
+
+      - name: Install dependencies
+        run: pip install -r requirements-dev.txt
+
+      - name: Lint with ruff
+        run: ruff check epub_safety_scanner.py test_epub_safety_scanner.py
+
+      - name: Format check with ruff
+        run: ruff format --check epub_safety_scanner.py test_epub_safety_scanner.py
+
+      - name: Type check with mypy
+        run: mypy epub_safety_scanner.py
+
+      - name: Security check with bandit
+        run: bandit -c pyproject.toml -r epub_safety_scanner.py
+
+      - name: Run tests
+        run: pytest -v