fix(sloppak/ws_highway): drums stay in picker and show correct hit count

lib/routers/ws_highway.py

@@ -478,12 +478,24 @@ def _evict_audio_cache():
             _evict_audio_cache()
 
         # Send song metadata
+        # For drum-only sloppaks the placeholder arrangement has 0 notes
+        # (drum_tab hits live separately).  Surface the real hit count so
+        # the UI shows e.g. "Drums (1922)" instead of "Drums (0)".
+        _DRUM_KEYWORDS = ("drum", "percussion")
+        _dt_hit_count = 0
+        if is_slop and loaded_slop is not None and loaded_slop.drum_tab is not None:
+            _dt_hit_count = len(loaded_slop.drum_tab.get("hits") or [])
         arr_list = [
             {
                 "index": i,
                 "name": a.name,
                 "smart_name": smart_names[i],
-                "notes": len(a.notes) + sum(len(c.notes) for c in a.chords),
+                "notes": (
+                    _dt_hit_count
+                    if (len(a.notes) == 0 and not a.chords and _dt_hit_count > 0
+                        and any(kw in (a.name or "").lower() for kw in _DRUM_KEYWORDS))
+                    else len(a.notes) + sum(len(c.notes) for c in a.chords)
+                ),
             }
             for i, a in enumerate(song.arrangements)
         ]

lib/sloppak.py

@@ -895,16 +895,21 @@ def load_song(
                     log.warning("sloppak: drum_tab %r failed validation: %s",
                                 drum_tab_rel, reason)
 
-    # Drum-only sloppak: every GP track was percussion, so it ships a
-    # drum_tab but no pitched arrangements. The highway WS rejects an empty
-    # arrangements list with "No arrangements found" *before* it serves the
-    # drum_tab, leaving the drums unplayable even in the drum highway.
-    # Synthesize a minimal placeholder arrangement so the stream proceeds and
-    # the drum_tab reaches the drum highway. It carries no notes (the guitar
-    # highway just shows an empty board) and, when the manifest omits a
+    # Drum sloppak: when a drum_tab is present but no existing arrangement is
+    # a drum part, synthesize a minimal placeholder so the drums appear in the
+    # arrangement picker and the drum_tab reaches the drum highway.  The editor
+    # strips drum arrangements out of the manifest (converting them to
+    # drum_tab), so without this a drum+bass sloppak would show only Bass in
+    # the picker with no way to reach the drums.  It carries no notes (the
+    # guitar highway just shows an empty board) and, when the manifest omits a
     # duration, derives a song length from the last drum hit so the timeline
     # isn't zero-length.
-    if not song.arrangements and drum_tab_data is not None:
+    _DRUM_KEYWORDS = ("drum", "percussion")
+    _has_drum_arr = any(
+        any(kw in (getattr(a, "name", "") or "").lower() for kw in _DRUM_KEYWORDS)
+        for a in song.arrangements
+    )
+    if not _has_drum_arr and drum_tab_data is not None:
         if song.song_length <= 0:
             # validate_drum_tab() intentionally does NOT type-check individual
             # hits (they're sanitized at WS-stream time), so a hit may carry a