Add workflow for publishing to Test PyPI

New workflow can be manually triggered via workflow_dispatch to publish
to Test PyPI (https://test.pypi.org) using secrets.TEST_PYPI_TOKEN.

This allows testing the package installation and distribution before
publishing to the production PyPI.

Usage:
  Go to Actions → Publish to Test PyPI → Run workflow

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: ryan-williams

.github/workflows/publish-test-pypi.yml

@@ -0,0 +1,56 @@
+name: Publish to Test PyPI
+
+on:
+  workflow_dispatch:
+
+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 uv
+        uses: astral-sh/setup-uv@v5
+
+      - name: Install dependencies
+        run: |
+          uv pip install --system -e .
+          uv pip install --system pytest
+
+      - name: Run tests
+        run: pytest tests/ -v
+
+  publish-test-pypi:
+    needs: test
+    runs-on: ubuntu-latest
+    permissions:
+      id-token: write
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Set up Python
+        uses: actions/setup-python@v5
+        with:
+          python-version: '3.11'
+
+      - name: Install uv
+        uses: astral-sh/setup-uv@v5
+
+      - name: Build package
+        run: |
+          uv pip install --system build
+          python -m build
+
+      - name: Publish to Test PyPI
+        uses: pypa/gh-action-pypi-publish@release/v1
+        with:
+          repository-url: https://test.pypi.org/legacy/
+          password: ${{ secrets.TEST_PYPI_TOKEN }}