Add local candidate validation

docs/roadmap/implementation.md

@@ -538,7 +538,7 @@ internal package documentation.
 
 ## Stage 5: Capture and validate one local candidate
 
-Status: Pending. Depends on Stage 4.
+Status: Complete. Depends on Stage 4.
 
 1. Implement stable-version syntax, clean `main` and index/worktree inspection,
    captured HEAD, profile snapshot/note loading, title identity, and unused local
@@ -558,6 +558,13 @@ HEAD, callback failure, and a callback changing HEAD or the worktree. Count a
 successful callback once. No test needs a publication service, and `Check`
 creates no tag or remote ref.
 
+Evidence: `internal/candidate` validates stable versions and committed note
+identity, captures a clean `main` commit, runs either the offline default or the
+configured callback once, and rechecks local mutable state. The public
+`releasekit.Check` API and `releasekit check` command provide the local
+diagnostic. Temporary Git repositories cover the acceptance cases; offline
+`go test -count=1 ./...` and `go run ./internal/apicheck` pass.
+
 ## Stage 6: Resolve and inspect the authoritative endpoint
 
 Status: Pending. Depends on Stage 5.