cmux Billing Read before changing billing, pricing, Stripe, Pro entitlement, checkout, webhook, or subscription code. Architecture map - creates Stripe Checkout Sessions for Pro when is set. It sets to the Stack user id, auto-creates an anonymous Stack user for signed-out buyers, and falls back to the legacy Stack purchase path when Stripe is unset or . The "already active" short-circuit lives here. - resolves the current Stack user, looks up their row, and creates a Stripe customer portal session returning to . - cancels or resumes the active Stripe Pro subscription; renders localized in-das…