Migrate validator tests to prepared plans

docs/roadmap/implementation.md

@@ -250,6 +250,12 @@ temporarily fail to compile; migrate them in Stage 9, not through a wrapper.
 
 ## Stage 9: Migrate Validator Tests To Prepared Execution
 
+**Completed:** Validator tests prepare plans before execution, distinguish
+preparation failures from invalid instances, and retain host/FS, portability,
+precision, freezing, and synchronous-cancellation coverage. The retired mock
+interface was removed. Go 1.27.3 `go test ./internal/validate ./internal/usecase`
+and `go test . -run 'Schema|Smoke'` passed.
+
 **Finding:** 4. **Scope:** `internal/validate` tests, particularly standard-validator and cancellation cases.
 
 1. Express meaningful direct-validation cases as plan preparation followed by