fix: add per-window X-axis orientation correction

The global PCA X-axis flip uses centroids averaged across all windows,
which can leave individual windows with left/right inverted (e.g. PvdA
appearing right of VVD in 2020). Mirror the existing per-window Y-axis
correction to also check and flip X values per window.

analysis/political_axis.py

@@ -427,9 +427,49 @@ def compute_2d_axes(
 
             axes["y_flipped_windows"] = y_flipped_windows
 
+            # Per-window X-axis correction: mirror the Y-axis logic above.
+            # The global X-flip uses centroids averaged across all windows, so
+            # individual windows can still have left/right inverted.
+            x_flipped_windows: set = set()
+            for wid, pos_dict in positions_by_window.items():
+                right_xs = []
+                left_xs = []
+                for ent, (x_val, y_val) in pos_dict.items():
+                    # direct party entity
+                    if ent in right_parties:
+                        right_xs.append(x_val)
+                    elif ent in left_parties:
+                        left_xs.append(x_val)
+                    # individual MP via metadata lookup
+                    party = _mp_party.get(ent)
+                    if party is not None:
+                        if party in right_parties:
+                            right_xs.append(x_val)
+                        elif party in left_parties:
+                            left_xs.append(x_val)
+
+                if right_xs and left_xs:
+                    right_avg = float(np.mean(right_xs))
+                    left_avg = float(np.mean(left_xs))
+                    if left_avg > right_avg:
+                        _logger.info(
+                            "Per-window X flip for window %s: "
+                            "right_avg_x=%.3f left_avg_x=%.3f — negating X",
+                            wid,
+                            right_avg,
+                            left_avg,
+                        )
+                        positions_by_window[wid] = {
+                            ent: (-x_val, y_val)
+                            for ent, (x_val, y_val) in pos_dict.items()
+                        }
+                        x_flipped_windows.add(wid)
+
+            axes["x_flipped_windows"] = x_flipped_windows
+
         except Exception:
             _logger.debug(
-                "Per-window Y orientation check failed; leaving per-window Y as-is"
+                "Per-window orientation check failed; leaving per-window axes as-is"
             )
 
         return positions_by_window, axes