Add "Play on Quest" button to header for non-Quest browsers

Shows a button that uses Meta's Web Launch to send the current URL
to the user's Quest headset. Hidden when already browsing on Quest.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

src/components/layouts/AppHeader.svelte

@@ -7,6 +7,15 @@
 
   // Show header when not in game
   $: visible = true; // We'll control visibility via parent component if needed
+
+  // Detect if running in Quest browser (don't show "Play on Quest" button if already on Quest)
+  const isQuestBrowser = typeof navigator !== 'undefined'
+    && /OculusBrowser/i.test(navigator.userAgent);
+
+  // Generate Meta Web Launch URL to send current page to Quest headset
+  $: webLaunchUrl = typeof window !== 'undefined'
+    ? `https://www.oculus.com/open_url/?url=${encodeURIComponent(window.location.href)}`
+    : '';
 </script>
 
 {#if visible}
@@ -16,6 +25,11 @@
         <h1 class="app-title">Space Combat VR</h1>
       </div>
       <nav class="header-nav">
+        {#if !isQuestBrowser}
+          <a href={webLaunchUrl} target="_blank" rel="noopener noreferrer" class="nav-link quest-link">
+            🥽 Play on Quest
+          </a>
+        {/if}
         <Link to="/controls" class="nav-link controls-link">🎮 Customize Controls</Link>
         <Link to="/leaderboard" class="nav-link leaderboard-link">🏆 Leaderboard</Link>
         <UserProfile />