paper-fetch Fetch the PDF for a paper given a DOI (or title). Tries multiple sources in priority order and stops at the first hit. Resolution order 1. Unpaywall — , read (skipped if not set) 2. Semantic Scholar — 3. arXiv — if present, 4. PubMed Central OA — if PMCID present, 5. bioRxiv / medRxiv — if DOI prefix is , query for the latest version PDF URL 6. Publisher direct (institutional mode only — ) — DOI-prefix → publisher PDF template (Nature / Science / Wiley / Springer / ACS / PNAS / NEJM / Sage / T&F / Elsevier). The caller's own subscription IP / cookies / EZproxy are what authorize t…