fix(gbfs): count docks, not PBSC's geofenced area, as station capacity

PBSC adds the bikes a station accepts in the geofenced area around its
docks to `capacity`, and reports that part as `geofenced_capacity`, which
is not a GBFS field. Bilbao Bizi publishes 39 docks as capacity 839 with
geofenced_capacity 800, so its stations would read as nearly empty: red,
drawn at maximum size, and carded "39 avail · 0 docks · 839 cap".
BiciMAD (671 of 678 stations, about twice the docks) and Dbizi (11 of 70)
do the same.

The shared parser now reads `capacity − geofenced_capacity` when the
extension is present and no larger than the total, so the layer, its
colour ratio and get_bike_share all see the docks. No registered system
changes: none of the 52 publishes a geofenced capacity above 0 (live
feeds, 2026-10-17, all 13,397 capacities identical).

Co-Authored-By: Claude Opus 5.5 <[email protected]>

src/sources/gbfsStations.js

@@ -81,6 +81,21 @@ function stationName(value) {
   return fallback;
 }
 
+/**
+ * Docks a station physically has. PBSC adds the bikes a station accepts in its
+ * geofenced area around the docks to `capacity` and reports that part as
+ * `geofenced_capacity` (not a GBFS field): Bilbao Bizi publishes 39 docks as
+ * capacity 839 with geofenced_capacity 800. Without the extension, or when it
+ * would exceed the total, `capacity` is read as given.
+ */
+function dockCapacity(raw) {
+  const capacity = toNonNegativeInteger(raw?.capacity);
+  const geofenced = toNonNegativeInteger(raw?.geofenced_capacity);
+  if (capacity == null || geofenced == null || geofenced > capacity)
+    return capacity;
+  return capacity - geofenced;
+}
+
 /**
  * Parse a GBFS station_information payload into a Map of station metadata.
  * Handles field-name variations across different GBFS providers
@@ -105,7 +120,7 @@ export function parseStationInformation(payload) {
       name: stationName(raw?.name) || stationName(raw?.short_name),
       lat,
       lon,
-      capacity: toNonNegativeInteger(raw?.capacity),
+      capacity: dockCapacity(raw),
       isInstalled: normalizeGbfsBool(raw?.is_installed, true),
       isRenting: normalizeGbfsBool(raw?.is_renting, true),
       isReturning: normalizeGbfsBool(raw?.is_returning, true),