Share immutable prepared execution metadata

docs/roadmap/implementation.md

@@ -352,6 +352,13 @@ selection, and mutation-isolation tests. Retain typed/numeric runtime cases.
 
 ## Stage 13: Share One Immutable Prepared Metadata Snapshot
 
+**Completed:** Prepared execution and internal details share one immutable,
+redacted snapshot; cleanup clears only execution payload references and the
+facade retains the outward copy. Obsolete copy-failure tests and the remaining
+retired direct-validation mock were removed. Go 1.27.3 `go test -race
+./internal/usecase . -run 'Prepared|Repair|SchemaFilePreparationDetachesLargeAnnotation'`
+passed, including lifecycle, details, schema, and repair cases.
+
 **Findings:** 5–6. **Files:** `internal/usecase/prepared_execution.go`,
 `prepared_execution.go`, `convert.go`, lifecycle/ownership tests.