Audio Wave: segments = user splits only (721 groups are markers, not segments)

Per clarification: the 721 group lines are clip markers, NOT segments. Segments come
ONLY from user split points, numbered globally from 1 — so the first split is seg1, not
seg23. 0 splits = 0 segments; N splits = N segments (seg k = point k-1 .. split k, tail
after the last split excluded). group lines still drawn (bold) + used for the group#.
JS matches (segPoints/nSegs). Empty summary now prompts to add splits.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

nodes/audio_wave_segments.py

@@ -108,19 +108,19 @@ def _parse_range(sel, n):
 
 
 def _segments_grouped(rms_n, times, duration, fps, group_frames, user_starts, beats):
-    """Segments = user split points UNION the fixed group boundaries (every group_frames
-    frames). The group lines are hard splits, so a segment never crosses one — the last
-    segment in a group ends exactly on the group boundary (e.g. frame 721)."""
+    """Segments come ONLY from the user's split points (the 721 group lines are just clip
+    markers, NOT segments). Points = [0] + splits; a segment runs between consecutive
+    points, so N splits -> N segments (the tail after the last split is not a segment).
+    Global numbering. `group` = which 721 group each segment starts in (for reference)."""
     gstep = max(group_frames, 1) / max(fps, 1)
     gbounds, k = [], 1
-    while k * gstep < duration - 1e-6:
+    while k * gstep < duration - 1e-6:                 # for drawing + the group number only
         gbounds.append(round(k * gstep, 3)); k += 1
-    allb = sorted({round(b, 3) for b in list(user_starts) + gbounds if 0 < b < duration - 1e-6})
-    starts = [0.0] + allb
+    pts = [0.0] + sorted({round(s, 3) for s in user_starts if 0 < s < duration - 1e-6})
     stages = ["establish", "build", "peak", "settle"]
     segs, bounds = [], [0.0]
-    for i, t0 in enumerate(starts):
-        t1 = starts[i + 1] if i + 1 < len(starts) else duration
+    for i in range(len(pts) - 1):                     # exclude the tail (last point -> end)
+        t0, t1 = pts[i], pts[i + 1]
         bounds.append(round(t1, 3))
         mask = (times >= t0) & (times < t1)
         e = float(rms_n[mask].mean()) if mask.any() else 0.0