Add Open Graph image and meta tags for link previews.

Matches opengsd.net OG style (grid, gradient headline, cyan header) at
pi.opengsd.net/og.png for social and messaging embeds.

Co-authored-by: Cursor <cursoragent@cursor.com>

index.html

@@ -4,6 +4,28 @@
     <meta charset="UTF-8" />
     <meta name="viewport" content="width=device-width, initial-scale=1.0" />
     <title>GSD Pi Config</title>
+    <meta
+      name="description"
+      content="Browser editor for GSD Pi — configure preferences.md, models.json, and agent settings, then download for your machine."
+    />
+    <meta property="og:type" content="website" />
+    <meta property="og:site_name" content="Open GSD" />
+    <meta property="og:title" content="GSD Pi Config — Configure. Edit. Download." />
+    <meta
+      property="og:description"
+      content="Browser editor for GSD Pi — configure preferences.md, models.json, and agent settings, then download for your machine."
+    />
+    <meta property="og:image" content="https://pi.opengsd.net/og.png" />
+    <meta property="og:image:width" content="1200" />
+    <meta property="og:image:height" content="630" />
+    <meta property="og:url" content="https://pi.opengsd.net/" />
+    <meta name="twitter:card" content="summary_large_image" />
+    <meta name="twitter:title" content="GSD Pi Config — Configure. Edit. Download." />
+    <meta
+      name="twitter:description"
+      content="Browser editor for GSD Pi — configure preferences.md, models.json, and agent settings, then download for your machine."
+    />
+    <meta name="twitter:image" content="https://pi.opengsd.net/og.png" />
     <link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/geist@1.3.1/dist/fonts/geist-sans/style.css" />
     <link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/geist@1.3.1/dist/fonts/geist-mono/style.css" />
   </head>