Install command aliases atomically

docs/roadmap/implementation.md

@@ -1,6 +1,6 @@
 # Application-owned aliases implementation plan
 
-Status: in progress; Stages 1–4 completed.
+Status: in progress; Stages 1–5 completed.
 
 ## Authority, baseline, and scope
 
@@ -378,6 +378,13 @@ versus runnable operand space; valid longer aliases beneath `r → run`; failed
 registration after a snapshot was used. Explicitly reject
 `promptkit test full → promptkit test all` under a `test KIND` fixture.
 
+**Completed:** Replaced direct registry mutation with a candidate that validates
+the complete canonical tree and normalized routing rules before publishing.
+Alias chains and termination, missing or operand-bearing targets, canonical
+source and operand collisions, duplicate idempotence, later command conflicts,
+and failed-batch preservation are covered. Verified with
+`go test ./... -count=1`.
+
 ## Stage 6: Compile effective flag aliases during installation
 
 **Work**