CI: retry release publishing through transient GitHub API errors The v2.8.2 tag run hit a GitHub API 503 during gh release create; the fallback then assumed "create failed" meant "release exists" and died on gh release upload against a nonexistent release. Now: check existence explicitly with gh release view, retry the whole publish up to 5 times 30s apart, and only fail after that. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>