fix: arxiv_refs — an arXiv API outage must turn the workflow red #142

Overview

arxiv_refs.yml ran green through the 2026-09-14..18 arXiv outage. Commits 0c3e2dc and 772d725 already added ArxivAPIError, the retry ladder, the api_failed stat and return 1, but the workflow pipes the script through tee without pipefail, so the non-zero exit is still discarded.

Plan

• Workflow: set -o pipefail, record the exit status, keep validate/commit of partial progress, then fail the job with an ::error::.
• Script: injectable sleep for the ladder; unparseable body → ArxivAPIError; http.client.HTTPException is transient; unattempted stat; None documented as "arXiv answered, no unique match" only.
• Witness test: injected HTTPError(429) is an API failure, never a non-match nor a NOTE-mark.
• Confirmed from git history: nothing was NOTE-marked in the outage window.

Original Prompt

Mind: draft/bug/pyautomemory/arxiv_refs_swallows_every_api_error_silently.md