Per-mode stop clustering thresholds

Rail stations get generous thresholds to merge all platform/entrance
duplicates; bus stays conservative:
  metro: 200m    -> 91 stops -> 44 markers (0 duplicates)
  s_tog: 400m   -> 76 stops -> 30 markers (0 duplicates)
  regional: 500m -> 27 stops ->  9 markers (0 duplicates)
  bus: 100m      -> 1610 stops -> 781 markers

stop_cluster_m is now a dict keyed by mode in styling.yaml.

copenhagen/scripts/render.py

@@ -196,7 +196,7 @@ def plot_stations(ax, stations, styling, active_styles):
     if not cfg.get("show", True):
         return
     marker_styles = set(cfg.get("styles", ["metro", "s_tog", "regional"]))
-    cluster_m = cfg.get("stop_cluster_m", 50)
+    cluster_cfg = cfg.get("stop_cluster_m", {})
     mk = cfg.get("marker", {})
     sizes = mk.get("size", {})
     shape = mk.get("shape", "circle")
@@ -220,11 +220,12 @@ def plot_stations(ax, stations, styling, active_styles):
     zord = styling["zorder"]
     top_z = max(zord.values()) + 1  # all markers above all lines
     for s in sorted(pts_by_style, key=lambda k: zord.get(k, 0)):
+        threshold = cluster_cfg.get(s, 50) if isinstance(cluster_cfg, dict) else cluster_cfg
         # cluster same-name stations to one marker; keep unnamed as-is
         centroids = []
         for name, coords in names_by_style[s].items():
             if name and len(coords) > 1:
-                centroids.extend(cluster_stops(coords, cluster_m))
+                centroids.extend(cluster_stops(coords, threshold))
             else:
                 centroids.extend(coords)
         sz = sizes.get(s, 3.0)
@@ -244,7 +245,8 @@ def plot_bus_stops(ax, stops, styling, active_styles):
     if bus.empty:
         return
 
-    cluster_m = cfg.get("stop_cluster_m", 50)
+    cluster_cfg = cfg.get("stop_cluster_m", {})
+    cluster_m = cluster_cfg.get("bus", 50) if isinstance(cluster_cfg, dict) else cluster_cfg
     mk = cfg.get("marker", {})
     sizes = mk.get("size", {})
     sz = sizes.get("bus", 1.5)