Fetch and parse a site's llms.txt (llmstxt.org) — the LLM-era robots.txt. Give any page URL; it resolves the origin's /llms.txt, and returns the H1 title, the blockquote summary, and every section's links ([title](url): notes). Also probes /llms-full.txt and reports its size. A site without one returns {found:false} (a 200, still useful). The fetch is SSRF-checked. Bonus signal in /v1/site-profile.