A stored og:image isn't proof it renders: signed/hotlink-protected URLs (e.g.
the Guardian's i.guim.co.uk) 401 on a direct browser load, so they counted
toward coverage yet always fell back. Now fetch_og_image confirms the image
truly returns 200 + image/* (requested no-referrer, same SSRF-safe redirect
handling) before storing it. Add prune_broken_images() to clear already-stored
URLs that no longer load, so coverage is honest and those cards show the
placeholder cleanly. The browser onerror→placeholder remains the final safety net.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
thejayman77
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