Sitemap config tightened, stale zombie endpoint force-overwritten

An old sitemap endpoint was lingering in the build output from a previous version — pointing at routes that no longer existed. Search engines were occasionally serving the zombie URLs instead of the current sitemap.

The new build forces an overwrite of the stale endpoint and asserts the URL count is positive at build time. A silent empty sitemap or a leftover endpoint cannot ship anymore — the assertion blocks the deploy if either condition is hit.