fix: center hero nav primary button using CSS grid

Use a 3-column grid layout (1fr auto 1fr) to ensure the "Read the Spec"
button is perfectly centered regardless of the different widths of the
"About" and "FAQ" buttons on either side.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/components/Hero.astro

@@ -13,9 +13,9 @@ interface Props {
 const { version, versions, svgContent } = Astro.props;
 
 const navItems = [
-  { id: "about", label: "About" },
+  { id: "about", label: "About", align: "end" },
   { id: "spec", label: "Read the Spec", primary: true },
-  { id: "faq", label: "FAQ" },
+  { id: "faq", label: "FAQ", align: "start" },
 ];
 
 const baseClasses = `inline-flex items-center justify-center gap-2
@@ -29,6 +29,7 @@ const primaryClasses = `bg-sky-600 text-white
 const secondaryClasses = `text-gray-600 dark:text-neutral-400
   hover:bg-gray-100 hover:text-gray-950
   dark:hover:bg-neutral-800 dark:hover:text-neutral-50`;
+
 ---
 
 <section
@@ -133,7 +134,7 @@ const secondaryClasses = `text-gray-600 dark:text-neutral-400
     <!-- Navigation links -->
     <nav
       class="animate-fade-in-up delay-400
-             flex flex-nowrap items-center justify-center gap-2 sm:gap-4"
+             grid grid-cols-[1fr_auto_1fr] items-center gap-2 sm:gap-4"
     >
       {
         navItems.map((item) => (
@@ -142,6 +143,8 @@ const secondaryClasses = `text-gray-600 dark:text-neutral-400
             class:list={[
               baseClasses,
               item.primary ? primaryClasses : secondaryClasses,
+              item.align === "end" && "justify-self-end",
+              item.align === "start" && "justify-self-start",
             ]}
           >
             {item.label}