Add native configuration display

docs/cli.md

@@ -125,6 +125,28 @@ empty value was explicitly supplied, so a scope callback can map those inputs to
 its own ConfigKit load policy. Help and invalid syntax do not call scope
 providers.
 
+### Show effective configuration
+
+`config show` writes the provider's native effective YAML for one scope. Its
+default scope is `app`; `--format yaml` is accepted and YAML is the only initial
+format. Single-scope output is passed through unchanged, without a CommandKit
+header or document marker.
+
+```text
+example config show
+example config show --scope promptkit
+example config show --scope all
+```
+
+`--scope all` acquires every selected scope and checks each effective writer
+before writing output. It then emits one YAML document per scope in discovery
+order, with a `# scope: NAME` comment after each document marker. Existing native
+markers and leading comments are retained; documents without a marker receive
+one. Scope labels containing line control characters are quoted to keep them on
+one comment line. A provider failure leaves the output stream empty. A rendering
+or output failure may leave an aggregate prefix, and the outcome reports
+incomplete report delivery.
+
 ## Outcome status
 
 CommandKit usage failures use status `2`; operational failures use status `1`.