Add lakes, urban areas, land, roads; layer toggle system
New geodata layers from Natural Earth:
- Lakes (96KB) — Great Lakes, major reservoirs
- Urban areas (95KB) — metro area outlines
- Land polygons (225KB) — enhanced coastline detail
- Roads/highways (753KB) — major interstates, shown when zoomed
11-layer rendering stack with toggleable visibility:
1. Coastlines 2. Land 3. Lakes 4. Urban areas
5. Rivers 6. State boundaries 7. Roads (zoom-only)
8. City labels 9. Amtrak routes 10. Stations 11. Trains
Press 'l' to open layer panel, number keys toggle each layer.
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Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>