Mark PromptKit validation implementation complete

docs/roadmap/implementation.md

@@ -1,6 +1,6 @@
 # PromptKit request validation implementation plan
 
-Status: Stages 1–8 complete; implementation is ongoing.
+Status: Stages 1–9 complete; implementation is complete.
 
 ## Authority, scope, and baseline
 
@@ -528,3 +528,16 @@ Markdown links and anchors and Markdown whitespace checks passed.
 applicable evidence above passes, public documentation and module metadata are
 aligned, and the workspace is clean. No unresolved product or API decisions
 were identified in preparing this plan.
+
+**Completed:** 2026-10-12. All three workspace suites passed, followed by all
+three isolated `GOWORK=off`, `-mod=readonly` module suites. Module and test
+dependency listings confirm the core and ckconfig boundaries, and ckprompt
+selects released PromptKit v0.15.0. Temporary ckconfig and ckprompt module files
+used only version-specific local replacements for unpublished CommandKit
+prerequisites; their module and sum hashes were unchanged by readonly checks.
+Both successful composed validation commands emitted only the requested
+`prompt_id` and `valid: true`; the missing-topic command failed operationally at
+native required-artifact validation. The complete ckprompt suite also passed
+the nil-builder, typed-builder, partial-discovery, and native-error coverage.
+The selected PromptKit attribution matches v0.15.0, changed documentation links
+and whitespace checks passed, and no unrelated or generated changes remain.