brain-atlas: correct og:image alt text to match the whole-brain card

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Author: itayinbarr

brain-atlas/index.html

@@ -22,7 +22,7 @@
   <meta property="og:image" content="https://itayinbarr.github.io/brainproject/og-image.png" />
   <meta property="og:image:width" content="1200" />
   <meta property="og:image:height" content="630" />
-  <meta property="og:image:alt" content="A 3D brain rendered in Brain Atlas, with a structure selected and its anatomical details shown." />
+  <meta property="og:image:alt" content="The Brain Atlas interactive 3D brain on its deep-blue stage, alongside the control panel." />
 
   <!-- Twitter / X -->
   <meta name="twitter:card" content="summary_large_image" />