Demonstrate composed configuration comparison

docs/roadmap/implementation.md

@@ -1,6 +1,6 @@
 # Implement ConfigKit adoption and configuration comparison
 
-Status: implementation in progress; Stages 1–9 are complete.
+Status: implementation in progress; Stages 1–10 are complete.
 
 ## Scope and authority
 
@@ -506,9 +506,18 @@ different selections or loader inputs; PromptKit remains an independent capabili
    supplied to both sides can make their effective defaults equal. Include
    `--limit=0` when campaign inspection triggers the existing input check.
 
-**Completion evidence:** meaningful simple and composed diff reports, cache
-separation for different selections, unchanged representative PromptKit/domain
-commands, and a usage failure for unsupported `--scope promptkit` comparison.
+**Completion evidence — complete:** the composed example now loads its two local
+files through ConfigKit, applies explicitly supplied Campaign as a native
+`default_campaign` override, and caches successful Results by complete supplied
+selection and Campaign presence/value. Tests confirm the ordinary fixture diff
+reports `changes.default_campaign: autumn`, a shared `--campaign spring` override
+produces equal effective values, distinct file and supplied-campaign keys do not
+reuse the wrong result, equal keys may reuse, nil state bypasses caching, and
+failed loads are not retained. Representative engine validate/show/sources/
+explain, named prompt/profile inspection, and session restore commands continue
+to succeed without model calls. The PromptKit config scope remains unsupported
+by `config diff`; that selection returns a usage error. README commands and cache
+identity explanation are updated. `go test -count=1 ./...` passes in ckp.
 
 ## Stage 11: Reconcile operator, API, and consumer documentation