Implementation Plan

Add centre-dash constants and a pure native compiler routine based on the shared bidirectional segment model and junction-trimmed centreline.
Filter invalid, one-way, service, and control-marking-conflicting dashes; record actionable diagnostics for invalid geometry only.
Write center_lines.geojson, compilation/comparison counts, native build records, required-layer checks, and Blender material adapter mapping.
Add Workbench API state, Chinese toggle, summary count, rendering, and source evidence for a selected centre dash.
Add focused native and Workbench tests for generation, skips, control avoidance, provenance, and file/API contracts.
Run native/unit/workbench/build-stage tests, compile/check Nantaizi, then validate blender,cesium,preview --road-provider native without package.

Rollback

Choose --road-provider osm2streets; no legacy layer or published package is modified.