Verify self-contained schema preparation and submission

docs/roadmap/implementation.md

@@ -375,6 +375,10 @@ recursive/dynamic references, embedded dialects, and independent instances.
 validate/engine tests finish the schema transition. No local-only mode, bundler,
 new dialect, or release/publication prerequisite is introduced.
 
+Completion: schema-file option, frozen preparation, native submission, and
+external-reference rejection are covered through public APIs. Root, validation,
+and engine tests pass on Go 1.27.3; current schema guidance is aligned.
+
 ## Stage 14: Merge Provider Maps Into One Owned Lower Copy
 
 **Catalog:** 19. **Files:** configuration targets and focused overlay tests.