Music: six more dungeon pieces and six surface pieces with flute, harp, birdsong and wind

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/audio.rs

@@ -21,6 +21,8 @@ pub enum Category {
     Temple,
     Victory,
     Defeat,
+    Surface,       // above ground: flute, harp, birdsong
+    SurfaceBattle, // fighting above ground
 }
 
 // indices of all tracks of a category, in play order
@@ -221,7 +223,9 @@ mod tests {
         dc_audio_init(48000.0);
         let build = tracks_in(Category::Build);
         let battle = tracks_in(Category::Battle);
-        assert_eq!(build.len(), 15);
+        assert_eq!(build.len(), 19);
+        assert_eq!(tracks_in(Category::Surface).len(), 4);
+        assert_eq!(tracks_in(Category::SurfaceBattle).len(), 2);
         play_music(build[0], 0.0);
         let mut peak = 0.0f32;
         for k in 0..200 {