Verify effective listing ownership and concurrency

docs/roadmap/implementation.md

@@ -166,7 +166,12 @@ receive independent public values with the selected error behavior.
 
 ## Stage 3 — Verify Effective Membership, Ownership, And Concurrent Use
 
-**Status: Pending.** Depends on Stage 2.
+**Status: Complete (2026-10-09).** Verified with
+`go test -race ./internal/configuration ./internal/engine .` and
+`git diff --check`. External tests cover layered effective membership,
+maintained profiles, empty inventories, caller ownership, concurrent listing
+and inspection, captured sources, and the absence of execution work. Depends on
+Stage 2.
 
 **Scope:** focused additions to the external-package listing contract tests.
 Production edits are limited to defects those tests reveal.