Runtime config for a tenant host, as a script

Tenant-host reserved path, served on every project subdomain, branch host, and custom domain before routes, static lookup, and SPA fallback. Returns window.RUN402 = { project_id, api_base, anon_key, embedding, live }; (live is { path: '/_run402/live', tables: [...] } or null: the tables that emit change hints on this host) for the project the host resolves to at request time — a branch host answers for the branch, a transferred project answers with its rotated anon key — so a static page never needs a key copied into its HTML: <script src="/_run402/config.js"></script>. Cache-Control: public, max-age=60. Never carries service_key. Not served from api.run402.com.