Preserve safe failure categories in deployment polling

When a GitHub Actions verifier wraps Railway CLI deployment polling, preserve a sanitized failure category and process exit information instead of replacing every CLI failure with one generic lookup error. Otherwise transient provider failures, credential failures and local process errors become indistinguishable after the runner exits, preventing evidence-based recovery. Keep tokens and raw provider output out of logs; record bounded categories and safe target identifiers. This improves diagnosis but does not establish the cause of a historical failure when its original stderr was discarded.

Applies when: A release verifier polls an asynchronous deployment through a subprocess. Keywords: Railway GitHub Actions deployment polling CLI stderr sanitization diagnostics