feat: publish native road layer manifest

docs/native-road-package-v1.md

@@ -1,4 +1,8 @@
-# Native Road Package v1
+# Native Road Package v1.1
+
+`native-road-package/v1.1` adds a required `manifest.json` to the v1 output.
+Consumers may ignore this file when reading legacy v1 packages, but v1.1
+consumers must validate and consume it.
 
 `native-road-package/v1` defines the boundary between the host area pipeline
 and the native road compiler. The compiler accepts only the input below; it
@@ -35,6 +39,12 @@ shape and owns all path derivation.
 
 `outDir` contains these JSON documents:
 
+- `manifest.json`: `{ contract: "native-road-package/v1.1", areaId, layers }`.
+  `layers` declares exactly the twelve GeoJSON sources. Renderable entries have
+  `role` (`surface` or `marking`) and `materialLayer`; semantic entries have
+  `role: "semantic"` and no material. Optional `splitBy` contains one property
+  and exact-match cases plus one default case.
+
 - `compiled.json`: top-level keys are `schema`, `areaId`, `source`, `model`,
   `movements`, `trafficSignals`, `diagnostics`, and `layers`. `source` has
   `osm`, `overrides`, and `trafficSignals` paths.