useMapFly's zoomToLegendRow comment names readSourceFeatures, not the engine-private _data

The comment still said the code reads map.getSource()._data, which invites a copy
of the private field back in; the code reads through the shared helper that knows
both engines' source shapes.

library/composables/useMapFly.js

@@ -474,8 +474,9 @@ export function useMapFly(options = {}) {
     /**
      * zoomToLegendRow — uniform "click a legend row, fit the scope it represents."
      *
-     * Reads the full `language-families` source data via map.getSource()._data
-     * and evaluates the Mapbox filter expression in JS, bypassing the viewport
+     * Reads the full `language-families` source data through readSourceFeatures()
+     * (library/maps/pin-selection.js, which knows both engines' source shapes; never
+     * the engine-private `_data` directly) and evaluates the filter expression in JS, bypassing the viewport
      * clip that previously caused off-screen regions to silently no-op. fitBounds
      * is bidirectional — it zooms OUT to a wider region just as readily as it
      * zooms IN to a tight cluster, so Africa-row and North-India-cluster-row