Split Open Map Overlays into Sea Marks and Ski Pistes layers

Each overlay is now its own Infrastructure row instead of a chip on one
shared row: sea-marks (token 6) and ski-pistes (token 7), both
enabled-only, built by createOsmOverlayLayers() from one descriptor
list. Drops the option group and its share-codec defaults, gives each
layer its own name, voice entry and CURRENT-STATE row, and shifts the
token-ledger fixtures to the next free digit 8.

src/ui/layerNames.js

@@ -43,7 +43,8 @@ export const LAYER_NAME_KEYS = Object.freeze({
   'air-quality': msg('Air quality'),
   directions: msg('Directions'),
   'alpr-cameras': msg('ALPR Cameras'),
-  'osm-overlays': msg('Open Map Overlays'),
+  'sea-marks': msg('Sea Marks'),
+  'ski-pistes': msg('Ski Pistes'),
 });
 
 /** The layer panel's own English names, where they differ from the module's. */