Per-jurisdiction coverage rollup (OPEN — no key, not metered)

One row per jurisdiction: record counts by instrument type, the code edition held, and the verification stamps. Aggregated in the database — this endpoint must never be answered by paging the corpus, since inviting a caller to walk 31,800 records just to count them is exactly the bulk copy the record budget exists to prevent. Open for the same reason as /us-law/taxonomy: coverage is how you evaluate the dataset before paying for it.