Polish release notes and in-app help (#2070)

* feat(ui): improve changelog and help navigation

Make release notes easier to scan and reach from the app. Also keep the homepage marquee within the layout viewport so it cannot create horizontal scrolling.

* fix(website): reject duplicate release anchors

packages/website/src/components/landing-page.tsx

@@ -84,7 +84,7 @@ export function LandingPage({ title, subtitle }: LandingPageProps) {
       <PhoneShowcase />
 
       {/* Content section */}
-      <div className="bg-background">
+      <div className="landing-content bg-background">
         <main className="p-6 md:p-20 md:pt-40 max-w-5xl mx-auto">
           <div className="space-y-24">
             <SocialProofWall />