diag: increase zone logging threshold to 60 words

Box zones have 40-60 words, need to capture their diagnostics.

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

klausur-service/backend/grid_editor_api.py

@@ -366,8 +366,8 @@ def _build_zone_grid(
     # Cluster rows first (needed for column alignment analysis)
     rows = _cluster_rows(zone_words)
 
-    # Diagnostic logging for small zones (box zones typically)
-    if len(zone_words) <= 30:
+    # Diagnostic logging for small/medium zones (box zones typically have 40-60 words)
+    if len(zone_words) <= 60:
         import statistics as _st
         _heights = [w['height'] for w in zone_words if w.get('height', 0) > 0]
         _med_h = _st.median(_heights) if _heights else 20