feat(marketing-site): American Dream cover band + narrative weave

- Cover: publisher-style belly band across the lower book cover using a
  compressed banner (2.2MB screenshot -> 60KB WebP, resized to display
  needs), cropped via a width-locked <img> + percentage offset so the
  wordmark stays legible rather than getting zoomed/cropped sideways.
  Compass + wordmark compacted into a row to make room.
- Copy: the theme woven through Field Notes, Contents, the Founding
  Sponsor tier, and one direct FAQ entry -- mostly oblique, since the
  cover already states it explicitly. Hero/Recipe/Capture/Footer left
  untouched on purpose.

marketing-site/components/Letter.jsx

@@ -7,8 +7,9 @@ export default function Letter() {
           Most AI advice is either hype or theory — and neither survives contact with real
           work. We’re writing the guide we wish we’d had: workflows that <em>actually run</em>,
           with the <span className="mark">guardrails built in</span>, kept honest by the people
-          who use them every day. Fund the first edition, and you don’t just get the book — you
-          help decide what goes in it.
+          who use them every day. For a lot of us, mastering these tools isn’t optional
+          anymore — it’s how you build the life you’re working toward. Fund the first edition,
+          and you don’t just get the book — you help decide what goes in it.
         </p>
         <div className="sign reveal">
           <span className="scrawl">The co-authors</span>