Audit a site's HTTP security headers before embedding, scraping, or trusting it. Returns an A+ to F grade and 0–100 score with structured analysis of HSTS, CSP, X-Frame-Options, X-Content-Type-Options, Referrer-Policy, Permissions-Policy, and Cross-Origin headers, plus server-header disclosure. A defense-in-depth signal for agents reviewing a site's security posture — not a vulnerability scan.