Add /play share page and X share links.

Includes a UX test page and Vercel/Vite routing for share URLs.

vite.config.ts

@@ -11,8 +11,12 @@ export default defineConfig({
     rollupOptions: {
       input: {
         main: resolve(__dirname, 'index.html'),
+        // Existing pages (keep for backward compatibility)
         embed: resolve(__dirname, 'embed.html'),
         models: resolve(__dirname, 'models.html'),
+        // Sharing trial pages
+        play: resolve(__dirname, 'play.html'),
+        ux_test: resolve(__dirname, 'ux-test.html'),
       },
     },
   },