chore(task): archive 08-18-native-traffic-signal-parity

.trellis/tasks/archive/2026-08/08-18-native-traffic-signal-parity/implement.md

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+# Implementation Plan
+
+1. Define the native signal model/override artifact and migration adapter;
+   reuse existing generation, validation, and deterministic signal UID rules.
+2. Add QGIS import/export commands that translate
+   `traffic_signal_assemblies.geojson` to/from the native artifact without
+   making native compile depend on QGIS.
+3. Extend native compile/workbench state to expose signal assemblies, OSM
+   controls/arms, and derived runtime provenance.
+4. Add validated atomic signal save operations for generate, move, rotate,
+   delete, and field edits; preserve legacy ID compatibility.
+5. Add Workbench map styling, selection, editing controls, dirty state, save,
+   compile/reload, and clear error handling for signal assemblies.
+6. Ensure native Blender/Cesium/preview stages consume runtime signal data
+   generated from the native model, while legacy stages remain compatible.
+7. Add focused traffic-signal, Workbench, migration, and cross-layer round-trip tests;
+   run the existing legacy traffic-signal and preview suites.
+
+## Validation
+
+```bash
+npm run test:traffic-signals
+npm run test:preview-assets
+npm run test:road-workbench
+npm run road:compile -- --config config/areas/nantaizi-lake-innovation-valley.json
+npm run road:check -- --config config/areas/nantaizi-lake-innovation-valley.json
+```
+
+Manual acceptance must cover native-only generate/move/rotate/delete -> save ->
+recompile -> runtime JSON and preview, plus QGIS import/export compatibility;
+disabled signals must be omitted from runtime output.