Distinguish unpaved tracks from paved roads on both basemaps

Offline: fill in protomaps' "other" road-kind color (unset before,
so tracks/paths silently fell back to plain white against the cream
background); also fixes a dead "minor" theme key that was never read
by the actual paint expression (only minor_a/minor_b is), so ordinary
streets were quietly using the base theme's default yellow instead of
this app's cream.

Online: Liberty's own road_service_track layer merges paved service
roads with unpaved tracks into one color, which isn't safe to just
recolor brown (real driveways aren't unpaved). Clones it into a
second layer scoped to class=="track" only, dashed and dirt-brown,
matching the offline treatment without mislabeling paved service
roads.

TODO.adoc

@@ -26,7 +26,7 @@ independence from connectivity.
 * [ ] Custom vector style (MVT/MapLibre) using the NPS color palette — muted natural tones for forests, water, and contours — so POIs and routes stand out at high zoom
 ** [ ] Landuse & protections: distinct styling for national parks, nature reserves (translucent green/gray-green), military zones, and private land (important for wild camping)
 ** [ ] Elevation-tinted terrain combined with offline hillshade for a characteristic relief look
-** [ ] Road hierarchy: clearly distinguish paved roads from unpaved/gravel/track — critical for knowing if the camper can get there
+** [x] Road hierarchy: clearly distinguish paved roads from unpaved/gravel/track — critical for knowing if the camper can get there
 
 == Main menu reorganization (4 modules)
 

public/js/map.js

@@ -104,6 +104,32 @@ function patchOnlineStyle(style) {
     const patch = ONLINE_STYLE_PATCH[layer.id];
     if (patch) Object.assign((layer.paint ??= {}), patch);
   }
+  return insertTrackOnlyLayer(style);
+}
+
+// Liberty's own "road_service_track" layer paints service roads (paved
+// driveways/parking aisles) and actual unpaved tracks the same color —
+// fine for a general-purpose map, not for this app's "can the camper get
+// there" use case. The underlying OpenMapTiles data does carry `class:
+// "track"` separately from `"service"` (see the filter below), so rather
+// than recoloring the merged layer (which would mislabel paved driveways
+// as unpaved), this clones it into a second layer scoped to `class ==
+// "track"` only, dashed and dirt-brown — matching how the offline theme
+// already renders protomaps' own separate "other"/"path" road kind.
+// Surface-level only (excludes tunnel_/bridge_ variants): an unpaved track
+// in a tunnel or on a bridge is rare enough not to be worth a third layer.
+function insertTrackOnlyLayer(style) {
+  const index = style.layers.findIndex((layer) => layer.id === "road_service_track");
+  if (index === -1) return style;
+
+  const base = style.layers[index];
+  const trackOnly = {
+    ...base,
+    id: "road_track_only",
+    filter: ["all", base.filter, ["==", ["get", "class"], "track"]],
+    paint: { ...base.paint, "line-color": "#c9a66b", "line-dasharray": [2, 2] },
+  };
+  style.layers.splice(index + 1, 0, trackOnly);
   return style;
 }
 
@@ -181,8 +207,21 @@ const OFFLINE_THEME = {
   pedestrian: "#e9e2d8",
   highway: "#fdefbe", // real: Park Tiles' primary/highway road color
   major: "#fef7dd", // real: Park Tiles' secondary road color
-  minor: "#fffdf8",
+  // "minor" (singular) is never actually read by protomaps' own paint
+  // expressions — only the zoom-interpolated minor_a/minor_b pair is, so a
+  // plain "minor" key here was dead: ordinary streets were silently
+  // falling back to the base theme's default pale yellow instead of this
+  // app's cream.
+  minor_a: "#fffdf8",
+  minor_b: "#fffdf8",
   link: "#fef7dd",
+  // Distinct brown, not cream: protomaps' "other"/"path" kind is what a
+  // camper actually needs called out — unpaved tracks and footpaths,
+  // separate from paved minor_road/service (minor_service, left at the
+  // base theme's default since it's real driveways/parking aisles, not
+  // unpaved). Already rendered dashed by the theme itself; this just picks
+  // a real "dirt" tone instead of unstyled white.
+  other: "#c9a66b",
   boundaries: "#546619", // real: Park Tiles' park-boundary line color
 };