request camera permission on intro page load

Prompt for webcam access early so the permission dialog appears
before the user reaches the game. Stream is immediately stopped
after permission is granted.

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

src/pages/IntroPage.tsx

@@ -1,3 +1,4 @@
+import { useEffect } from 'react'
 import { useNavigate } from 'react-router-dom'
 import { ROUTE_PATHS } from '../app/route-paths'
 import { playSound, SFX_BUTTON_DEFAULT } from '../lib/sounds'
@@ -16,6 +17,12 @@ const UNR_URL = 'https://www.unr.edu'
 export function IntroPage() {
   const navigate = useNavigate()
 
+  useEffect(() => {
+    navigator.mediaDevices.getUserMedia({ video: true })
+      .then((stream) => stream.getTracks().forEach((t) => t.stop()))
+      .catch(() => {})
+  }, [])
+
   const goFullscreen = () => {
     document.documentElement.requestFullscreen().catch(() => {})
     navigate(ROUTE_PATHS.home)