Add GitHub Actions workflow for PyPI publishing

Supports:
- TestPyPI publishing via workflow_dispatch
- PyPI publishing on release
- OIDC trusted publisher (no tokens needed)

Signed-off-by: Claude Opus 4.5 <noreply@anthropic.com>
Signed-off-by: Deborah Jacob <deborah@botanu.ai>

Author: deborahjacob-botanu

.github/workflows/publish.yml

@@ -0,0 +1,81 @@
+# SPDX-FileCopyrightText: 2026 The Botanu Authors
+# SPDX-License-Identifier: Apache-2.0
+
+name: Publish to PyPI
+
+on:
+  release:
+    types: [published]
+  workflow_dispatch:
+    inputs:
+      target:
+        description: 'Target repository'
+        required: true
+        default: 'testpypi'
+        type: choice
+        options:
+          - testpypi
+          - pypi
+
+permissions:
+  contents: read
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+
+      - uses: actions/setup-python@v5
+        with:
+          python-version: "3.12"
+
+      - name: Install build dependencies
+        run: pip install build
+
+      - name: Build package
+        run: python -m build
+
+      - name: Upload artifacts
+        uses: actions/upload-artifact@v4
+        with:
+          name: dist
+          path: dist/
+
+  publish-testpypi:
+    needs: build
+    runs-on: ubuntu-latest
+    if: github.event_name == 'workflow_dispatch' && github.event.inputs.target == 'testpypi'
+    environment: testpypi
+    permissions:
+      id-token: write
+    steps:
+      - name: Download artifacts
+        uses: actions/download-artifact@v4
+        with:
+          name: dist
+          path: dist/
+
+      - name: Publish to TestPyPI
+        uses: pypa/gh-action-pypi-publish@release/v1
+        with:
+          repository-url: https://test.pypi.org/legacy/
+
+  publish-pypi:
+    needs: build
+    runs-on: ubuntu-latest
+    if: github.event_name == 'release' || (github.event_name == 'workflow_dispatch' && github.event.inputs.target == 'pypi')
+    environment: pypi
+    permissions:
+      id-token: write
+    steps:
+      - name: Download artifacts
+        uses: actions/download-artifact@v4
+        with:
+          name: dist
+          path: dist/
+
+      - name: Publish to PyPI
+        uses: pypa/gh-action-pypi-publish@release/v1