Add PromptKit smoke test adapter

docs/roadmap/implementation.md

@@ -1,6 +1,6 @@
 # Dependency upgrades, discovery, and smoke testing implementation plan
 
-Status: Stages 1–8 complete; Stage 9 is next.
+Status: Stages 1–9 complete; Stage 10 is next.
 
 ## Authority and baseline
 
@@ -492,6 +492,19 @@ No live provider or real credentials are needed.
 **Complete when:** one concrete smoke request reaches the native API through an
 independently optional, composable adapter.
 
+**Completed:** 2026-10-17. Added `SmokeRequest`, the independently optional
+`Suite.SmokeTest` callback, and `WithSmokeTesting`. The helper preserves other
+suite capabilities and issues, invokes an optional builder before loading,
+forwards its complete request unchanged, retains loader diagnostics, checks
+cancellation before acquisition, and returns the native report and error
+without filtering either. Focused tests cover nil-builder forwarding,
+authoritative builder output, context/input/state, builder failure before load,
+nil-loader issue retention, cancellation, loader diagnostics, and native error
+identity. PromptKit's injected-client fixture returned a report with nil error
+when the client returned an error, so public fixture evidence for a
+report-plus-error pair is unavailable; the adapter returns both native values
+directly. Focused adapter tests and `GOTOOLCHAIN=local go build ./...` passed.
+
 ## Stage 10: Implement faithful smoke YAML projection
 
 **Primary files:** private `smoke_report.go` and focused projection tests.