Add PyPI release workflow

Publishes to TestPyPI then PyPI on GitHub release creation.
Uses trusted publishing (OIDC) — no API tokens needed in secrets.
Tests run against all Python versions before publishing.

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

Author: dkijania

.github/workflows/release.yml

@@ -0,0 +1,73 @@
+name: Release to PyPI
+
+on:
+  release:
+    types: [published]
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        python-version: ["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: |
+          python -m pip install --upgrade pip
+          pip install -e ".[dev]"
+
+      - name: Run tests
+        run: pytest -v
+
+  publish-testpypi:
+    runs-on: ubuntu-latest
+    needs: test
+    environment: testpypi
+    permissions:
+      id-token: write
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Set up Python
+        uses: actions/setup-python@v5
+        with:
+          python-version: "3.12"
+
+      - name: Build package
+        run: |
+          pip install build
+          python -m build
+
+      - name: Publish to TestPyPI
+        uses: pypa/gh-action-pypi-publish@release/v1
+        with:
+          repository-url: https://test.pypi.org/legacy/
+
+  publish-pypi:
+    runs-on: ubuntu-latest
+    needs: publish-testpypi
+    environment: pypi
+    permissions:
+      id-token: write
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Set up Python
+        uses: actions/setup-python@v5
+        with:
+          python-version: "3.12"
+
+      - name: Build package
+        run: |
+          pip install build
+          python -m build
+
+      - name: Publish to PyPI
+        uses: pypa/gh-action-pypi-publish@release/v1