Migrate native PromptKit test fixtures

docs/roadmap/implementation.md

@@ -1,6 +1,6 @@
 # PromptKit v0.18.0 implementation plan
 
-Status: Stages 1–2 complete; Stages 3–7 remain.
+Status: Stages 1–3 complete; Stages 4–7 remain.
 
 ## Authority and execution
 
@@ -122,6 +122,8 @@ fixtures may still prevent the full test suite from running.
 
 ## Stage 3: Convert native engine fixtures
 
+**Complete.** Native fixtures use identified resource lists and explicit minimal bundle choices; focused engine-backed tests pass. Report path expectations remain for Stage 4.
+
 1. Inspect ckprompt test configurations outside the composed example (Stage 5),
    including embedded YAML, MapFS files, and programmatic mappings. Start with `adapterEngine` and
    `adapterEngineFrom` in `adapters_test.go`, then the requirements, validation,