docs: clarify music transition is a sequential fade, not cross-fade

Semesterprojekt/docs/music.md

@@ -5,7 +5,8 @@ Background music plays only in the Swing GUI. It is **data-driven and external**
 - Put `.ogg` (OGG Vorbis) files in a `music/` folder next to where you run the game.
   This folder is git-ignored and never bundled in the JAR.
 - A room plays a track via an optional `music:` field in `rooms.yaml`, e.g.
-  `music: manor-theme.ogg`. Entering a room with a different track cross-fades to it;
+  `music: manor-theme.ogg`. Entering a room with a different track fades the old one
+  out and the new one in (sequential, not an overlapping cross-fade);
   a room with no `music:` field fades to silence; the same track keeps playing
   seamlessly across rooms.
 - Volume is the **Music** setting (Off / Low / Medium / High) in the Settings menu,