Add ConfigKit validation and diagnostics

docs/cli.md

@@ -102,6 +102,29 @@ runtime context or acquire configuration. It reports the intersection between
 declared scope capabilities and installed handlers, so an operation is listed
 only when the corresponding command is available.
 
+### Validate configuration
+
+`config validate` loads and validates the selected scope. The default scope is
+`app`; `--scope all` validates every registered scope and is available when each
+scope declares validation. The command checks all selected capabilities before
+calling scope providers.
+Its default format is text; `--format yaml` emits a `scopes` sequence with
+`name` and `valid: true` for each scope that completed successfully.
+
+```text
+example config validate
+example config validate --scope promptkit --format yaml
+example config validate --scope all
+```
+
+Each successful scope is reported as `SCOPE: valid`. Aggregate validation stops
+at the first load or output failure; records from earlier successful scopes may
+already have been written. Provider warnings go to the diagnostic stream and do
+not alone make validation fail. `--config` and `--overlay` preserve whether an
+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.
+
 ## Outcome status
 
 CommandKit usage failures use status `2`; operational failures use status `1`.

docs/development.md

@@ -4,8 +4,9 @@ CommandKit currently contains adopted repository policies, accepted architectura
 decisions, implementation plans, identity and outcome primitives, typed command
 declarations, an instance-owned registry, a Cobra-backed routing and parsing
 adapter, public `App.Execute` coordination, and generated help/version commands.
-Configuration suite registration and scope discovery are implemented; the
-configuration operations remain pending. The
+Configuration suite registration, scope discovery, ConfigKit integration, and
+validation are implemented; other configuration and PromptKit operations remain
+pending. The
 [README](../README.md) provides project orientation; the
 [documentation policy](policy/documentation.md#canonical-ownership) assigns
 canonical documentation owners.

docs/roadmap/implementation.md

@@ -1,6 +1,6 @@
 # Initial CommandKit implementation plan
 
-Status: implementation underway; Stages 1-7 complete and Stages 8-14 pending.
+Status: implementation underway; Stages 1-8 complete and Stages 9-14 pending.
 
 Date: 2026-10-07.
 
@@ -551,7 +551,7 @@ sequenced in Stages 8-11.
 
 ## Stage 8: integrate ConfigKit and implement validation
 
-**Status:** pending. **Prerequisite:** Stage 7.
+**Status:** complete. **Prerequisite:** Stage 7.
 
 ```go
 func NewConfigKitScope[C, T any](name, summary string,
@@ -594,6 +594,16 @@ empty overlay callback input; warnings permit validation success; structured loa
 errors retain public identity and render once; all validates in order and stops
 on failure. Report/diagnostic short writes retain their writer errors.
 
+**Completion evidence:** added the ConfigKit scope adapter and grouped diagnostic
+writer. The adapter exposes native effective/source/explanation facets, captures
+success and `LoadError` diagnostics, and preserves loader errors. `config validate`
+now installs for declared scopes, preflights all requested capabilities, acquires
+in stable order, and emits success records incrementally in text or YAML. Checks
+cover ConfigKit defaults, overlay, recorded resolution, absent/empty selections,
+warning success, load-error identity and single presentation, aggregate stop
+behavior, and report/diagnostic short writes. `go test ./...` passes; README,
+development orientation, and CLI reference describe the implemented boundary.
+
 ## Stage 9: implement native effective YAML display
 
 **Status:** pending. **Prerequisite:** Stage 8.