ci: add GitHub Actions workflows for PR checks and PyPI publishing

- pull_request.yml: lint (ruff) + test on PRs to master
- publish.yml: build and publish to PyPI on pushes to master
  (uses Trusted Publishing via PyPI publisher)

.github/workflows/publish.yml

@@ -0,0 +1,20 @@
+name: Publish
+on:
+  push:
+    branches: [master]
+jobs:
+  build-and-publish:
+    runs-on: ubuntu-latest
+    permissions:
+      id-token: write
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v7
+      - name: Setup UV
+        uses: astral-sh/setup-uv@v8.2.0
+        with:
+          python-version: "3.13"
+      - name: Run uv build
+        run: uv build
+      - name: Publish to PYPI
+        uses: pypa/gh-action-pypi-publish@release/v1

.github/workflows/pull_request.yml

@@ -0,0 +1,40 @@
+name: Pull Request
+on:
+  pull_request:
+    branches: [master]
+jobs:
+  lint:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v7
+      - name: Setup UV
+        uses: astral-sh/setup-uv@v8.2.0
+        with:
+          python-version: "3.13"
+      - name: Run uv sync
+        run: uv sync
+      - name: Run linter
+        run: uv run ruff check src/ tests/
+      - name: Run formatter
+        run: uv run ruff format --check src/ tests/
+  test:
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        python-version: ["3.10", "3.11", "3.12", "3.13"]
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+      - name: Setup UV
+        uses: astral-sh/setup-uv@v8.2.0
+        with:
+          python-version: ${{ matrix.python-version }}
+      - name: Run uv sync
+        run: uv sync
+      - name: Load sandbox credentials
+        env:
+          SANDBOX_ENV: ${{ secrets.SANDBOX_ENV }}
+        run: printf '%s\n' "$SANDBOX_ENV" > .env
+      - name: Run tests
+        run: uv run pytest tests/ -q