Add effective diff consumer examples

docs/roadmap/implementation.md

@@ -352,7 +352,7 @@ and the existing nil-result/`LoadError` load contract.
 
 ## Stage 9 — Demonstrate both consumer workflows
 
-Status: planned. Scope: maintained examples and their behavior tests.
+Status: complete. Scope: maintained examples and their behavior tests.
 
 1. Add a small complete example under `examples/consumers` that loads two caller-
    selected files with one definition, handles each load error, calls `Diff`, and
@@ -374,6 +374,15 @@ Validate: `go test ./examples/consumers`, `go test . -run '^ExampleDiff$'` when
 added, and the everyday check. Done: applications can implement the motivating
 workflows without internal imports or their own structural comparison.
 
+Evidence: `go test ./examples/consumers`, `go test . -run '^ExampleDiff$'`,
+and `./scripts/check.sh` passed. Temporary-file coverage exercises both
+caller-selected loads and base-versus-selected-overlay comparison. The overlay
+case verifies a recorded derived URL after resolution, a retained lower-priority
+port, bilateral redaction and `HiddenChanged` for a nested secret-reference
+change, deterministic consumer formatting, and no credential disclosure. The
+presenter uses snapshot presence and record membership without interpreting the
+redaction marker; no full-context rendering supplements the diff records.
+
 ## Stage 10 — Reconcile documentation and audit the complete feature
 
 Status: planned. Scope: current-behavior documentation, integration audit, and