Record the completed public facade refactor

docs/roadmap/implementation.md

@@ -316,6 +316,20 @@ Acceptance: compatibility review finds no unauthorized changes, all required
 validation passes, documentation matches the implemented architecture, and the
 refactor is ready for independent review before subsequent feature work.
 
+### Completion
+
+- [x] Compared the final exported GoDoc inventory with the recorded baseline;
+  no exported API difference was found. Reviewed the root source diff to
+  confirm that fields, tags, interfaces, method sets, error identities, and
+  formatting contracts remain unchanged.
+- [x] Confirmed that root production code retains boundary conversion and error
+  mapping only, while internal engine assembly delegates to the existing runner
+  and specialized packages retain their focused behavior coverage.
+- [x] Reviewed architecture, component inventory, source, runner, and model
+  client documentation for current ownership and local links.
+- [x] Completed the full offline maintainer validation workflow and repository
+  hygiene review.
+
 ## Open Questions
 
 None requiring a product decision for this scope. The refactor preserves the