[jbsq] use the correct magic bytes for long note charts

CHANGELOG.md

@@ -7,6 +7,13 @@ Format based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 
 I try to follow [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## v2.0.3
+### Fixed
+- [jbsq] Use "IJSQ" as magic bytes when dumping charts with hold notes so that
+  the hold symbol shows up properly on a song's preview pane when the song is
+  downloaded from the Gift Store or transferred via local matching
+  (contributed by [kis](https://gitlab.com/_kis))
+
 ## v2.0.2
 ### Fixed
 - Bump the required versions of

jubeatools/formats/konami/jbsq/dump.py

@@ -55,7 +55,7 @@ def make_jbsq_chart(events: List[konami.Event], notes: List[AnyNote]) -> constru
         density_graph=densities,
         events=jbsq_events,
     )
-    jbsq_chart.magic = b"JBSQ"
+    jbsq_chart.magic = choose_magic_bytes(notes)
     return jbsq_chart
 
 
@@ -100,3 +100,14 @@ def compute_density_graph(events: List[konami.Event], end_time: int) -> List[int
         res.append(density_byte)
 
     return res
+
+
+def choose_magic_bytes(notes: List[AnyNote]) -> bytes:
+    # The magic bytes are actually checked by the app to decide whether or not
+    # to display the "hold note" icon next to the song jacket
+    if any(isinstance(note, song.LongNote) for note in notes):
+        return b"IJSQ"
+    else:
+        # Could have also used IJBQ here instead, I don't know if that makes a
+        # difference
+        return b"JBSQ"