Turn the menu theme up

0.3 -> 0.5. Nothing else is playing over the menus, so it can sit forward.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

audio.js

@@ -107,7 +107,7 @@ export const zombieMusic = () => loopBed('zombie-mode', 800, 0.2);         // ba
 // MUSIC, not an atmosphere bed, so the low end is the point. Started at boot so it is already
 // running by the time the title is on screen; on a phone the autoplay policy holds the context
 // suspended until the first tap, and it becomes audible then (see loopBed).
-export const menuMusic = () => loopBed('background-music', 30, 0.3);
+export const menuMusic = () => loopBed('background-music', 30, 0.5);
 
 // duck a bed to silence (out=true) or back to its base level over `secs` — the sudden-death duel mutes the music
 function fadeBed(file, out, secs = 0.7) {