Retire completed roadmaps for release preparation

docs/roadmap/deferred.md

@@ -32,3 +32,20 @@ concrete consumer evidence, compatibility review, and an explicit design change.
 Built-in sibling inheritance using `extends` is implemented as described in the
 [configuration contract](../config.md#sibling-inheritance). It is distinct from
 inheritance between selected overlay files, which remains excluded above.
+
+## Deferred performance experiments
+
+The completed performance audit left these internal optimization candidates for
+separate investigation:
+
+- branch-local explanation replay instead of the current whole-tree replay;
+- redesigning the private metadata-copy handoff while preserving detached public
+  records;
+- caching schema descriptors across loads; and
+- indexing complex contributor-trace membership while preserving its equality
+  rules and compact linked traces.
+
+These are not committed implementation work. Reconsider them with evidence that
+the benefit justifies the ownership, retained-memory, or equivalence risks. The
+completed audit and implementation evidence are preserved in Git history at
+`8e91a2b` under `docs/roadmap/`.