# Implementation Plan

1. Add reusable template-placement helper to the existing turn-arrow module,
   preserving its supported-asset gate and output ring shape.
2. Extend the native compiler with lane-separator, repeated road-direction
   arrow, and explicit-turn-arrow polygon generation plus source diagnostics
   and layer persistence.
3. Extend native output records/counts and Blender adapter mappings. Reuse
   existing `lane_separators` and `lane_arrows_webscale` materials only.
4. Add Workbench layers, toggles, selection/provenance inspector entries, and
   preserve the existing Workbench-only direction triangle behavior.
5. Add focused fixtures for supported turn placement, unsupported maneuver,
   short approach skip, and separator geometry; run native/workbench/build
   stage tests.
6. Build Nantaizi with `blender,cesium,preview --road-provider native`, inspect
   the final preview, and confirm no `package/` publication occurred.

## Validation

```bash
npm run test:native-road
npm run test:road-workbench
npm run test:turn-lane-arrows
npm run test:build-stages
npm run road:compile -- --config config/areas/nantaizi-lake-innovation-valley.json
npm run build:area -- --config config/areas/nantaizi-lake-innovation-valley.json \
  --stages blender,cesium,preview --road-provider native
```

Rollback is selecting `--road-provider osm2streets`; no existing output path
is replaced.