Look up a public GitHub repository by "owner/name" slug. Returns full name, owner, description, homepage, default branch, primary language, topics, license (SPDX key + name), counts (stars / forks / watchers / open issues / subscribers / network), size, timestamps (created/updated/pushed), visibility, has-issues/projects/wiki/discussions flags. Unauthenticated GitHub access is rate-limited to 60 req/hour per server IP — returns 429 UPSTREAM_RATE_LIMIT when the bucket is empty.