Add native configuration display

docs/roadmap/implementation.md

@@ -1,6 +1,6 @@
 # Initial CommandKit implementation plan
 
-Status: implementation underway; Stages 1-8 complete and Stages 9-14 pending.
+Status: implementation underway; Stages 1-9 complete and Stages 10-14 pending.
 
 Date: 2026-10-07.
 
@@ -606,7 +606,7 @@ development orientation, and CLI reference describe the implemented boundary.
 
 ## Stage 9: implement native effective YAML display
 
-**Status:** pending. **Prerequisite:** Stage 8.
+**Status:** complete. **Prerequisite:** Stage 8.
 
 1. Implement `config show`; its only initial format is yaml (default and explicit).
    Single scope writes Effective.WriteEffective directly to Out with no envelope,
@@ -633,6 +633,16 @@ labels and native values. Cover an already marked native document, missing/null/
 empty structures, a second acquisition failure with no prefix, and a writer failure
 after output begins. These protect selected behavior, not encoder whitespace.
 
+**Completion evidence:** installed `config show` when a scope declares it, with
+YAML as its only format. Single-scope output passes through the native effective
+writer; aggregate output acquires and checks every view before emitting framed
+native documents in scope order. Existing markers, leading comments and YAML
+directives are retained, including explicit document termination where needed
+between directive-bearing documents. Checks cover native single-scope bytes,
+aggregate document decoding and values, invalid formats, acquisition failure with
+empty output, and incomplete delivery after a writer failure. `go test ./...`
+passes; README, development orientation, and CLI reference describe the feature.
+
 ## Stage 10: implement source inventory reports
 
 **Status:** pending. **Prerequisite:** Stage 9.