Show dimension markup for first chord using refs within same chord

- Add _find_ref_in_same_chord() to find adjacent pitches within the same chord
- Update first chord handling to show refs to other pitches in chord

src/transcriber.py

@@ -387,6 +387,33 @@ def _find_ref_and_dim_diff(
     return adjacent[0]
 
 
+def _find_ref_in_same_chord(pitch_idx: int, chord_pitches: list) -> tuple[int, int]:
+    """Find ref (other pitch index) and dim_diff within the same chord.
+
+    Args:
+        pitch_idx: index of the current pitch in the chord
+        chord_pitches: list of hs_arrays for all pitches in the chord
+
+    Returns:
+        (ref, dim_diff) tuple where ref is index of adjacent pitch in same chord
+    """
+    current_hs = chord_pitches[pitch_idx]
+    adjacent = []
+
+    for idx, other_hs in enumerate(chord_pitches):
+        if idx == pitch_idx:
+            continue
+        if _is_adjacent(current_hs, other_hs):
+            dim_diff = _compute_dim_diff(current_hs, other_hs)
+            adjacent.append((idx, dim_diff))
+
+    if not adjacent:
+        return -1, 0
+
+    adjacent.sort(key=lambda x: abs(x[1]))
+    return adjacent[0]
+
+
 def output_chords_to_music_data(chords, fundamental=55, chord_duration=4):
     """Convert output_chords.json format to generic music data.
 
@@ -425,8 +452,7 @@ def output_chords_to_music_data(chords, fundamental=55, chord_duration=4):
             current_hs_array = current_hs[voice_idx]
 
             if prev_chord is None:
-                ref = -1
-                dim_diff = 0
+                ref, dim_diff = _find_ref_in_same_chord(voice_idx, current_hs)
             elif current_hs_array == prev_chord[voice_idx]:
                 ref = -1
                 dim_diff = 0