The form posts to admin's signup and the slug preview goes: there is no
instance at this point, and previewing one promises something the
submission does not create. Creating the instance is now a step in the
portal, which the page's What happens next panel spells out.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
The signup form now posts instance_name, matching sitesvc.
Also restores site/next-env.d.ts. Its /// <reference> directives had been
stripped, which removed the Next.js type environment and failed the build
with "Cannot find name 'Promise'". Same cause as the agent's missing build
constraint.