Adopt ConfigKit overlays for pipeline selection

docs/roadmap/implementation.md

@@ -1,6 +1,6 @@
 # Implementation Plan: Audita v2 and Shared Provider Credentials
 
-Status: Not started.
+Status: In progress.
 
 ## Scope and working instructions
 
@@ -164,7 +164,12 @@ extraction fingerprints, references, force, resume, or chunk-cache behavior.
 
 ## Stage 1: Adopt ConfigKit v0.4.0 and pipeline overlays
 
-Status: Not started.
+Status: Complete (2026-09-25).
+
+Verification: `go test ./internal/config ./internal/app ./internal/manifest`,
+`go test ./...`, `go test ./internal/doccheck`,
+`go test ./internal/config -run '^TestExamplesLoadAndValidate$'`, and
+`git diff --check` passed.
 
 Preparation: ConfigKit v0.4.0 release notes and selected-overlay migration guide
 in `../ConfigKit/docs/`; Narratio `internal/config/pipeline_configkit.go`,