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/voice/layerManifest.js

@@ -72,21 +72,16 @@ const layers = [
     noQuery: 'published third-party intel placemarks; not analyst records',
   },
   {
-    id: 'osm-overlays',
-    aliases: [
-      'open map overlays',
-      'map overlays',
-      'sea marks',
-      'seamarks',
-      'nautical charts',
-      'openseamap',
-      'ski pistes',
-      'ski slopes',
-      'snow map',
-      'opensnowmap',
-    ],
+    id: 'sea-marks',
+    aliases: ['seamarks', 'nautical charts', 'buoys', 'openseamap'],
     context: false,
-    noQuery: 'raster tile overlays; no countable records',
+    noQuery: 'raster tile overlay; no countable records',
+  },
+  {
+    id: 'ski-pistes',
+    aliases: ['ski slopes', 'ski runs', 'snow map', 'opensnowmap'],
+    context: false,
+    noQuery: 'raster tile overlay; no countable records',
   },
   {
     id: 'flights',