feat(docs): accessibility + SEO fixes

Accessibility: global :focus-visible outlines, id="main-content" on all
custom pages. SEO: robots.txt, JSON-LD WebSite schema, Geist font preload.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: emrul

docusaurus.config.ts

@@ -32,6 +32,35 @@ const config: Config = {
 
   onBrokenLinks: 'throw',
 
+  headTags: [
+    {
+      tagName: 'link',
+      attributes: {
+        rel: 'preload',
+        as: 'font',
+        type: 'font/ttf',
+        href: '/fonts/geist/Geist-VariableFont_wght.ttf',
+        crossorigin: 'anonymous',
+      },
+    },
+    {
+      tagName: 'script',
+      attributes: { type: 'application/ld+json' },
+      innerHTML: JSON.stringify({
+        '@context': 'https://schema.org',
+        '@type': 'WebSite',
+        name: 'Aster Docs',
+        url: 'https://docs.aster.site',
+        description: 'Documentation for Aster — peer-to-peer RPC framework with cryptographic identity.',
+        publisher: {
+          '@type': 'Organization',
+          name: 'Aster',
+          url: 'https://aster.site',
+        },
+      }),
+    },
+  ],
+
   // Even if you don't use internationalization, you can use this field to set
   // useful metadata like html lang. For example, if your site is Chinese, you
   // may want to replace "en" with "zh-Hans".

src/css/custom.css

@@ -2470,3 +2470,13 @@ html[data-theme='light'] .asterSignalPanel__meta span {
   0%, 48% { opacity: 1; }
   49%, 100% { opacity: 0; }
 }
+
+/* ── Accessibility: focus-visible ──────────────────────────────────────── */
+a:focus-visible,
+button:focus-visible,
+[role="button"]:focus-visible,
+[tabindex]:focus-visible {
+  outline: 2px solid var(--aster-teal);
+  outline-offset: 3px;
+  border-radius: 4px;
+}

src/pages/index.tsx

@@ -364,7 +364,7 @@ export default function Home(): React.JSX.Element {
     <Layout
       title="Machines authenticate to machines, on behalf of users."
       description="Peer-to-peer RPC framework with identity in the connection. Capability-based auth, cross-language wire format, built on iroh QUIC.">
-      <main className="asterHome">
+      <main id="main-content" className="asterHome">
         <section className="asterHero">
           <div className="container asterHero__container">
             <div className="asterHero__content">

src/pages/terminal-demo.tsx

@@ -8,7 +8,7 @@ export default function TerminalDemo(): React.JSX.Element {
     <Layout
       title="Terminal Animation Demo"
       description="Isolated Aster terminal animation prototype driven by a polished asciicast recording.">
-      <main className="asterHome asterTerminalDemoPage">
+      <main id="main-content" className="asterHome asterTerminalDemoPage">
         <section className="asterSection">
           <div className="container">
             <div className="asterTerminalDemoPage__header">

src/pages/terminal-landing.tsx

@@ -91,7 +91,7 @@ export default function TerminalLanding(): React.JSX.Element {
     <Layout
       title="Terminal Landing Prototype"
       description="Alternative Aster landing page concept using a focused terminal animation hero.">
-      <main className="asterHome asterTerminalLandingPage">
+      <main id="main-content" className="asterHome asterTerminalLandingPage">
         <section className="asterTerminalLandingHero">
           <div className="container asterTerminalLandingHero__container">
             <div className="asterTerminalLandingHero__copy">

static/robots.txt

@@ -0,0 +1,4 @@
+User-agent: *
+Allow: /
+
+Sitemap: https://docs.aster.site/sitemap.xml