/download is now /sign-up — clearer about what the page does

What shipped

• •/download (and /download/free) permanently redirect to /sign-up — every external link still resolves.
• •Anonymous CTA in the top right now reads 'Sign up free' instead of 'Get Orbit'. The link still routes to the same form.
• •Copy across the site reframed: 'sign up to download' rather than 'download Orbit'. Makes it clear that the free account also gives you saved tool history (naming conventions, scored subject lines, IP-warm plans, more), course progress with completion badges, and LinkedIn-shareable certifications.
• •Sitemap, FAQ, llms.txt, and chat search results all updated to point at /sign-up.