Add arid tracks and swap in new spacestation music

- Add three arid theme tracks (arid-01/02/03) and a new spacestation-03 track
- Point station 15-17 at the new arid tracks instead of reusing lava
- Add spacestation variant 2 and reorder existing station frame mappings

data/music.json

@@ -34,14 +34,15 @@
     "12": "assets/music/lava-01.mp3",
     "13": "assets/music/lava-02.mp3",
     "14": "assets/music/lava-03.mp3",
-    "15": "assets/music/lava-01.mp3",
+    "15": "assets/music/arid-01.mp3",
-    "16": "assets/music/lava-02.mp3",
+    "16": "assets/music/arid-02.mp3",
-    "17": "assets/music/lava-03.mp3",
+    "17": "assets/music/arid-03.mp3",
     "18": "assets/music/capital-neutral-01.mp3"
   },
   "_stationFrames_comment": "stationFrames = the loop that plays on a deep-space station's surface — keyed by the spacestations.png VARIANT frame (the same key its landing/takeoff clips use, data/landing.json → stationVideos), so a station hums the track matching the art it is drawn with. Empty for now (a station surface is silent) until the station tracks are authored — add one line per variant when they land.",
   "stationFrames": {
-    "0": "assets/music/spacestation-01.mp3",
+    "0": "assets/music/spacestation-02.mp3",
-    "1": "assets/music/spacestation-02.mp3"
+    "1": "assets/music/spacestation-01.mp3",
+    "2": "assets/music/spacestation-03.mp3"
   }
 }