osmWorkflow/.trellis/tasks/archive/2026-08/08-14-native-road-lane-markings/implement.md

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

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.