Add skip-existing to PyPI publish for idempotent re-runs

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: lightsofapollo

.github/workflows/release.yml

@@ -110,6 +110,7 @@ jobs:
         uses: pypa/gh-action-pypi-publish@release/v1
         with:
           packages-dir: dist/
+          skip-existing: true
 
   publish-cuda:
     name: Publish CUDA wheels to PyPI