Demonstrate PromptKit comparison and catalogs

docs/roadmap/implementation.md

@@ -1,6 +1,6 @@
 # Implement PromptKit comparison and catalogs
 
-Status: Stages 1–8 complete; remaining stages are planned.
+Status: Stages 1–9 complete; remaining stages are planned.
 
 ## Scope and authority
 
@@ -531,6 +531,24 @@ Run example tests and the complete ckprompt suite. Existing ordinary scope
 operations, named reports, app comparison, and the domain command must work with
 the upgraded dependency.
 
+**Completion evidence (2026-10-12)**
+
+- Replaced the obsolete negative PromptKit diff test with a public composed-app
+  invocation that compares the before/after fixtures using the spring selector
+  and decodes the native change under the spring profile. Updated the after
+  fixture's spring model to make that comparison meaningful. The application
+  diff test still checks the changed default and now also checks the model value
+  under an explicit spring override.
+- Added composed public invocations for both catalogs with config and campaign
+  selection. Tests decode the YAML and find the configured `briefing` version
+  and selected `autumn` profile without pinning PromptKit's full catalog.
+- Updated the example README with copyable PromptKit diff/catalog commands and
+  described how the selection-aware loader and sample cache behave. Existing
+  ordinary scope operations, named reports, app comparison/cache behavior, and
+  session command coverage remain in place.
+- `GOTOOLCHAIN=local go test -count=1 .` passed in the composed example, and
+  `GOTOOLCHAIN=local go test -count=1 ./...` passed in `integrations/ckprompt`.
+
 ## Stage 10: Reconcile canonical documentation and capability status
 
 **Outcome:** current documentation describes delivered behavior and separates