Add a site to audit; your human completes its checkout

Add a site to audit. A site is the unit of purchase: the answer carries checkout_url, the site's checkout link your human opens to subscribe on Whop (card on file; $79/month per site, billed every 30 days; 3-day free trial on a workspace's first site; later sites are charged at checkout; the answer's billing.trial_offered says which this site's checkout is). Nothing is charged until your human pays, and nothing crawls until then: the first crawl starts by itself when the subscription lands, so do not call crawls_start on an unpaid site. It starts a billing path, so it asks for confirmation: call it with dry_run: true first, then with confirm: true. Hand checkout_url to your human word for word; never open it yourself. Adding a site you already have answers that site (and, while it is unpaid, a fresh checkout). Next: sites_get once your human has paid.