feat: add native road compiler workbench

.trellis/tasks/08-13-native-road-compiler/implement.md

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+# Implementation Plan
+
+1. Add area output/config normalization and command entrypoints for the native
+   compiler, preserving existing stage behavior and paths.
+2. Implement a shared OSM road parser and canonical road/endpoints model with
+   source provenance, explicit versus inferred properties, and stable IDs.
+3. Implement v1 override schema, validation, load/apply behavior, atomic save,
+   and focused unit tests.
+4. Implement projected road segment geometry, supported T/cross junction
+   detection, native GeoJSON artifact emission, diagnostics, and comparison
+   summary.
+5. Implement a dependency-free local workbench server and browser UI with
+   selection, provenance display, v1 parameter/topology editing, explicit save,
+   compile/reload, and error states.
+6. Add native compiler tests using focused fixtures plus nantaizi analysis;
+   run existing relevant Node tests to confirm legacy behavior remains intact.
+7. Compare nantaizi and at least one supplied problematic OSM sample. Record
+   metrics, unsupported cases, and follow-up work in task research.
+
+## Validation
+
+```bash
+npm run road:compile -- --config config/areas/nantaizi-lake-innovation-valley.json
+npm run road:workbench -- --config config/areas/nantaizi-lake-innovation-valley.json
+npm run test:build-stages
+npm run test:preflight
+npm run test:preview-assets
+```
+
+Browser validation includes loading the workbench, editing a road parameter,
+saving, verifying the override file, recompiling, reloading, and confirming
+provenance identifies the saved override.