Pick the most-canonical link to expose in markdown one-liners.

Create the label if it doesn't exist; ignore errors if it does.

GET arxiv URL with exponential backoff on 429 / timeout / 5xx. arXiv asks API consumers to set a descriptive User-Agent including a contact a

Look for prior watcher-opened issues (by label) and harvest arxiv ids from their bodies.

Fetch recent papers in `category` submitted on/after `since` (UTC).

All arxiv ids referenced by items/*.json (Paper_Link), as bare e.g. '2503.20215'.

Try `gh api` first (authenticated, higher rate limit); fall back to anonymous curl.

Extract (owner, repo) from a GitHub URL. Tolerates trailing slashes, /tree/* paths, and .git suffixes.