# Implementation Plan

1. Add native provider/default-stage contracts and explicit legacy provider routing.
2. Make package publication and stage manifests consume native runtime artifacts.
3. Replace preview's hard dependency on osm2streets lane/network/intersection files with a native
   route adapter and optional-route behavior.
4. Audit Blender, Cesium, preview, diagnostics, and area config for native-path legacy reads; retain
   only the Workbench's optional, clearly labeled osm2streets reference layer.
5. Update README/config/spec documentation and add dependency-boundary regression tests.
6. Run native-only tests with legacy directories absent, then run focused legacy compatibility tests.
7. Run area compile/check plus available Blender/Cesium/preview validation; record any environment-only
   limitation without weakening native contracts.

## Validation

```bash
npm run test:native-road
npm run test:traffic-signals
npm run test:road-workbench
npm run test:preview-assets
npm run road:compile -- --config config/areas/nantaizi-lake-innovation-valley.json
npm run road:check -- --config config/areas/nantaizi-lake-innovation-valley.json
node --check scripts/build-area.js
```

The final gate must also exercise a native-only config/output directory without QGIS/osm2streets
intermediates and assert package/runtime/preview outputs.