Verify native PromptKit request validation

docs/roadmap/implementation.md

@@ -1,6 +1,6 @@
 # PromptKit request validation implementation plan
 
-Status: Stages 1 and 2 complete; implementation is ongoing.
+Status: Stages 1–3 complete; implementation is ongoing.
 
 ## Authority, scope, and baseline
 
@@ -196,6 +196,17 @@ selected builder-before-loader lifecycle.
 **Complete when:** the adapter's native authority, builder forwarding, failure
 handling, and cancellation boundaries have meaningful public-boundary evidence.
 
+**Completed:** 2026-10-12. Added real-engine adapter coverage for native success,
+missing required input, invalid profile, and an unloadable file reference. The
+builder test supplies a required inline artifact and verifies context, selection,
+typed input, and state reach both callbacks; validation succeeds without a model
+call. Tests cover nil engines, retained `*configkit.LoadError` diagnostics and
+identity, cancellation before and after building, cancellation during and after
+loading, and PromptKit's native artifact-load category when an artifact reader
+returns cancellation. Focused adapter tests and
+`GOTOOLCHAIN=local go test -count=1 ./...` passed from
+`integrations/ckprompt`.
+
 ## Stage 4: Implement the validate command and requirements group composition
 
 **Primary files:** `integrations/ckprompt/command.go`, a new private