chore(task): archive 08-17-native-road-control-markings

.trellis/tasks/archive/2026-08/08-17-native-road-control-markings/implement.md

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+# Implementation Plan
+
+1. Extend the native OSM parse/model with marked crossing-node evidence while
+   preserving existing road IDs and parser behavior.
+2. Add native crossing clustering, tangent resolution from directed lane
+   centerlines, stripe geometry, safe stop-line placement, and source
+   diagnostics.
+3. Persist the two new layers in `compile-native-roads.js`, comparison counts,
+   native build records, required native layer checks, and existing Blender
+   material mappings.
+4. Add Workbench API/state fields, Chinese layer toggles, selection evidence,
+   and summary counts while retaining scene-preview behavior.
+5. Add focused fixtures for marked and unmarked crossings, duplicate cluster
+   handling, a missing native-lane diagnostic, and output layer contracts.
+6. Run native/unit/workbench/build-stage tests, compile/check Nantaizi, then
+   build `blender,cesium,preview --road-provider native` without `package/`.
+
+## Validation
+
+```bash
+npm run test:native-road
+npm run test:road-workbench
+npm run test:build-stages
+npm run road:compile -- --config config/areas/nantaizi-lake-innovation-valley.json
+npm run road:check -- --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 legacy output path is
+changed.