feat(loader): per-room music field + demo rooms.yaml entries

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Semesterprojekt/src/test/java/thb/jeanluc/adventure/loader/RoomMusicTest.java

@@ -0,0 +1,28 @@
+package thb.jeanluc.adventure.loader;
+
+import org.junit.jupiter.api.Test;
+import thb.jeanluc.adventure.loader.dto.RoomDto;
+import thb.jeanluc.adventure.model.Room;
+
+import java.util.List;
+import java.util.Map;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+class RoomMusicTest {
+
+    @Test
+    void musicFieldIsCarriedOntoRoom() {
+        RoomDto dto = new RoomDto("r", "Room", "d",
+                Map.of(), List.of(), List.of(), null, null, null, "theme.ogg");
+        Room room = RoomFactory.shellFromDto(dto);
+        assertThat(room.getMusic()).isEqualTo("theme.ogg");
+    }
+
+    @Test
+    void absentMusicIsNull() {
+        RoomDto dto = new RoomDto("r", "Room", "d", Map.of(), List.of(), List.of());
+        Room room = RoomFactory.shellFromDto(dto);
+        assertThat(room.getMusic()).isNull();
+    }
+}