Cover validation command lifecycle and grammar

docs/roadmap/implementation.md

@@ -1,6 +1,6 @@
 # PromptKit request validation implementation plan
 
-Status: Stages 1–4 complete; implementation is ongoing.
+Status: Stages 1–5 complete; implementation is ongoing.
 
 ## Authority, scope, and baseline
 
@@ -311,6 +311,19 @@ YAML output into a fresh value; avoid output-prefix or key-order assertions.
 **Complete when:** the new capability obeys the selected standard grammar,
 availability, capture, and invocation-lifetime contracts.
 
+**Completed:** 2026-10-12. Added validation-only availability, namespace
+collision and root-only placement coverage; construction/install/help/version
+callback timing; eager callback and selector capture; exact standard request,
+selector, empty-presence, repeated-assignment, first-`=` file, and duplicate
+last-wins behavior; repeated-invocation isolation; usage preflight; input-check
+failure ordering; and nil-pointer zero-value factories. A missing required
+captured selector is a usage outcome before `Suite.CheckInput`, state creation,
+or provider work. Under the existing `CaptureFlags`/`prepareSuiteInput` flow,
+`Suite.NewInput` runs before `FlagValues.ApplyTo` reports that missing selector.
+Focused validation command tests and
+`GOTOOLCHAIN=local go test -count=1 ./...` passed from
+`integrations/ckprompt`.
+
 ## Stage 6: Cover native command outcomes and report delivery
 
 **Primary files:** validation command tests and small real-engine fixtures.