github-linkcheck-404-throttle-false-negativelisted

# GitHub Link-Check 404-Throttle False Negative ## Problem Link checkers hit github.com issue/PR pages anonymously. GitHub's anti-scraping throttle answers some of those requests with **404, not 429** — so a checker configured to tolerate rate limits (`--accept 200,206,429`, the common lychee setup) still reports a hard "dead link" on a URL that resolves fine in a browser or via the API. During a GitHub platform incident the same false-404s appear repo-wide at once. ## Context / Trigger Conditions - CI job red with lines like: `[404] https://github.com/<owner>/<repo>/issues/47 | Rejected status code: 404 Not Found` - The links are same-forge issue/PR URLs, often many at once. - The failing files were not touched by the change under test. - Bonus tell for the outage variant: a second unrelated job (CodeQL, actions analysis) fails in the same run, or the Actions API itself returns 503. ## Solution 1. **Verify the links via the API, not the page**: `gh api repos/<owner>/<repo>/issues/<n> --jq '.number,.state'` — if this returns, the link is alive and the 404 is throttle/outage noise. 2. **Check platform status before diagnosing the repo**: `curl -s https://www.githubstatus.com/api/v2/status.json` — an `indicator` of `major`/`critical` explains everything at once; stop repo-side diagnosis. 3. **Re-run the failed job after the throttle window / incident passes**: `gh run rerun <run-id> --failed`. Note: a rerun is refused while the workflow is still `in_