# Native traffic signal parity with QGIS

## Goal

Move traffic-signal ownership from the QGIS editing chain into the native road
compiler and Workbench. Existing QGIS signal assemblies remain import/export
compatibility data during migration, but native overrides become the long-term
source for generation, editing, and Blender/Cesium/preview delivery.

## Confirmed Facts

- QGIS currently edits `traffic_signal_assemblies.geojson`; this is the
  migration input/output contract, not the desired long-term authority.
- `scripts/reimport-gpkg.js` validates and reimports that legacy layer.
- `scripts/build-area.js` currently derives runtime `traffic_signals.json` from
  the edited assemblies; the native path must replace this dependency.
- Existing native road layers do not read traffic-signal artifacts. Historical
  native Cesium work intentionally omitted signal runtime assets.
- Stable signal identity and editable fields already include `signal_uid`,
  enabled state, source/control/approach IDs, arm direction, pose, mast reach,
  and phase-group/runtime data.

## Requirements

- R1: Native compile/workbench must own a versioned area-local signal model and
  override artifact, with an explicit one-time/import compatibility path from
  existing QGIS assemblies.
- R2: Workbench state must expose signal provenance and the existing editable
  signal fields using stable IDs, and support generating, moving, rotating,
  and deleting signal assemblies.
- R3: Native compile and preview delivery must generate runtime signal data
  directly from the native model, preserving enabled/disabled state, arm
  direction/pose, and phase-group data without requiring QGIS.
- R4: A compatibility adapter must import/export the existing QGIS assembly
  format during migration and preserve legacy signal IDs where possible.

## Scope Boundary

- Native signal model and overrides are the long-term source of truth.
- QGIS GeoJSON/GeoPackage support is transitional compatibility only; do not
  make native compile depend on QGIS or regenerate native edits from QGIS.
- Do not redesign signal geometry, timing logic, or vehicle behavior in this
  task.

## Acceptance Criteria

- [ ] A native compile/reopen round trip preserves edited signal assemblies,
  stable IDs, enabled state, and provenance without QGIS running.
- [ ] The Road Workbench can generate, inspect, move, rotate, and delete signal
  assemblies, then save durable edits without breaking QGIS reimport.
- [ ] Native Blender/Cesium/preview consume runtime signal data generated from
  the native model, including disabled signals being omitted from runtime.
- [ ] QGIS import/export compatibility and legacy build stages continue to
  pass while the migration adapter exists.
- [ ] Nantaizi has documented native-only and QGIS-imported round trips.