feat: Add GitHub Actions workflows for CI and automated PyPI publishing

.github/workflows/python-release.yml

@@ -0,0 +1,41 @@
+name: Python Release
+
+on:
+  release:
+    types: [published]
+
+jobs:
+  test:
+    uses: ./.github/workflows/python-test.yml
+
+  publish:
+    needs: test
+    runs-on: ubuntu-latest
+    environment:
+      name: pypi
+      url: https://pypi.org/project/gtfs-diff-engine/
+    permissions:
+      id-token: write  # Required for PyPI Trusted Publisher (OIDC)
+      contents: read
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Set up Python
+        uses: actions/setup-python@v5
+        with:
+          python-version: "3.12"
+
+      - name: Install build backend
+        run: |
+          python -m pip install --upgrade pip
+          pip install build
+
+      - name: Build distributions
+        run: |
+          python -m build
+
+      - name: Publish to PyPI
+        uses: pypa/gh-action-pypi-publish@release/v1
+        with:
+          verbose: true

.github/workflows/python-test.yml

@@ -0,0 +1,29 @@
+name: Python Tests
+
+on:
+  workflow_call:
+  workflow_dispatch:
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+      # Oldest and latest supported versions — sufficient to catch compatibility issues
+        python-version: ["3.10", "3.12", "3.14"]
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Set up Python
+        uses: actions/setup-python@v5
+        with:
+          python-version: ${{ matrix.python-version }}
+
+      - name: Install package
+        run: |
+          python -m pip install --upgrade pip
+          pip install -e ".[dev]"
+
+      - name: Run tests
+        run: python -m pytest tests/ -v

README.md

@@ -27,7 +27,7 @@ pip install gtfs-diff-engine
 For a development (editable) install with test dependencies:
 
 ```bash
-git clone https://github.com/your-org/gtfs-diff-engine
+git clone https://github.com/MobilityData/gtfs-diff-engine
 cd gtfs-diff-engine
 pip install -e ".[dev]"
 ```
@@ -240,6 +240,30 @@ pip install -e ".[dev]"
 pytest tests/ -v
 ```
 
+## Releasing a New Version
+
+1. **Bump the version** in `pyproject.toml`:
+   ```toml
+   [project]
+   version = "x.y.z"
+   ```
+
+2. **Commit and push** the version bump to `main`.
+
+3. **Create a GitHub Release** via the GitHub UI (or `gh release create`):
+   - Set the tag to `vx.y.z` (e.g. `v0.2.0`)
+   - Write a release title and notes summarising changes
+   - Click **Publish release**
+
+4. **The publish workflow fires automatically.** The [`Publish to PyPI`](.github/workflows/publish.yml) GitHub Actions workflow triggers on release publication, builds the package, and pushes it to PyPI via [Trusted Publisher (OIDC)](https://docs.pypi.org/trusted-publishers/) — no API token required.
+
+5. **Verify** the new version appears on [https://pypi.org/project/gtfs-diff-engine](https://pypi.org/project/gtfs-diff-engine) and is installable:
+   ```bash
+   pip install gtfs-diff-engine==x.y.z
+   ```
+
+> **One-time PyPI setup:** A maintainer must configure the repository as a Trusted Publisher on PyPI before the first automated release. Go to the [gtfs-diff-engine PyPI project](https://pypi.org/manage/project/gtfs-diff-engine/settings/publishing/), add a publisher for `MobilityData/gtfs-diff-engine`, workflow `publish.yml`, environment `pypi`.
+
 ## License
 
 See [LICENSE](LICENSE).