refactor: consume external road compiler

.trellis/spec/pipeline/index.md

@@ -18,6 +18,7 @@
 | 改复合路口几何（`buildComplexJunctionGeometry`、车道控制避让、人行道转角） | [CLI 与阶段](./cli-and-stages.md#可编辑信号设施与运行时锚点的跨阶段消费) 的复合路口小节 |
 | 改预览页生成 | [../preview/](../preview/index.md) |
 | 声称"纯重构，产物不变" | [产物一致性指南](../guides/artifact-parity-guide.md) |
+| Native road compiler CLI、输入或完成标记 | [编译器契约指针](./native-road-package.md) |
 
 ---
 

.trellis/spec/pipeline/native-road-package.md

@@ -0,0 +1,9 @@
+# Native Road Compiler Contract
+
+The native-road package is maintained in the private `road-compiler` repository:
+
+`https://git.app.que01.top/que01/road-compiler`
+
+This host consumes the exact git tag recorded in `package.json` and lockfile. The host owns area configuration normalization and writes `RoadCompilerInput`; the compiler owns the `native-road-package/v1` file contract and CLI. Production code must invoke the installed compiler CLI through `scripts/lib/road-compiler-cli.js`, not import compiler source files or read `packages/road-compiler`.
+
+The completion marker is `NATIVE_ROAD_COMPILE_DONE <json>`. `build-area.js` validates the marker's count, JSON payload, area id, output path, process status, and signal before starting Blender.