fix: shrink overlapping neighbors after narrow column expansion

When a narrow column expands into neighbor space, the neighbor's
boundaries must be adjusted to avoid overlap. After expansion, left
neighbor's right edge and right neighbor's left edge are trimmed to
match the expanded column's new boundaries, with words re-assigned.

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

klausur-service/backend/cv_vocab_pipeline.py

@@ -1976,6 +1976,41 @@ def expand_narrow_columns(
                 "ExpandNarrowCols: col %d (%.1f%% → %.1f%%) x=%d w=%d words=%d",
                 i, orig_pct, g.width / content_w * 100, g.x, g.width, g.word_count)
 
+            # --- Shrink overlapping neighbors to match new boundaries ---
+            # Left neighbor: its right edge must not exceed our new left edge
+            if i > 0:
+                left_nb = geometries[i - 1]
+                nb_right = left_nb.x + left_nb.width
+                if nb_right > g.x:
+                    left_nb.width = g.x - left_nb.x
+                    if left_nb.width < 0:
+                        left_nb.width = 0
+                    left_nb.width_ratio = left_nb.width / content_w if content_w > 0 else 0.0
+                    # Re-assign words
+                    nb_left_rel = left_nb.x - left_x
+                    nb_right_rel = nb_left_rel + left_nb.width
+                    left_nb.words = [wd for wd in word_dicts
+                                     if nb_left_rel <= wd['left'] < nb_right_rel]
+                    left_nb.word_count = len(left_nb.words)
+
+            # Right neighbor: its left edge must not be before our new right edge
+            if i + 1 < len(geometries):
+                right_nb = geometries[i + 1]
+                my_right = g.x + g.width
+                if right_nb.x < my_right:
+                    old_right_edge = right_nb.x + right_nb.width
+                    right_nb.x = my_right
+                    right_nb.width = old_right_edge - right_nb.x
+                    if right_nb.width < 0:
+                        right_nb.width = 0
+                    right_nb.width_ratio = right_nb.width / content_w if content_w > 0 else 0.0
+                    # Re-assign words
+                    nb_left_rel = right_nb.x - left_x
+                    nb_right_rel = nb_left_rel + right_nb.width
+                    right_nb.words = [wd for wd in word_dicts
+                                      if nb_left_rel <= wd['left'] < nb_right_rel]
+                    right_nb.word_count = len(right_nb.words)
+
     return geometries