Creates a new app in the authenticated tenant. runtime defaults to nodejs if omitted.
Returns 409 duplicate_app_name when the tenant already has an app with the supplied name.
Returns 402 entitlement_required with entitlement: "max_apps", limit, and current when the tenant has hit their app quota — agents can branch on this to prompt a tier upgrade.
Application ID for tenant scoping
API key (sk_agentmark_*)
App created.