Add ConfigKit overlay migration to the plan

docs/roadmap/audita.md

@@ -1,4 +1,4 @@
-# Adopt Audita v2
+# Adopt Audita v2 and ConfigKit v0.4.0
 
 Status: agreed scope; implementation has not started.
 
@@ -13,6 +13,9 @@ so operators define each secret once and explicitly share it with the downstream
 applications that need it. This is a clean cutover without backward-compatibility
 shims.
 
+Adopt ConfigKit v0.4.0 and use “overlay” consistently for Narratio's selected
+pipeline configuration, distinct from downstream LLM model profiles.
+
 Production runs use Audita's default reporting configuration: Narratio passes
 neither `--debug` nor `--reporting=false`. Normal reports remain available without
 enabling debug diagnostics. Adding debug reporting through Narratio's testing
@@ -73,6 +76,34 @@ duplicate Audita's complete validation logic.
 
 ## Configuration and invocation migration
 
+### ConfigKit and pipeline overlays
+
+Upgrade Narratio's ConfigKit dependency from v0.3.1 to v0.4.0. ConfigKit's
+selected-configuration terminology changes from profile to overlay: the Go API
+uses `Options.Overlay`, `LayerOverlay`, and `CodeOverlay*`; source layers and
+diagnostic codes use `overlay` and `overlay.*`. Composition, precedence, secret
+resolution, and lifecycle semantics otherwise remain unchanged.
+
+Narratio's pipeline-selection interface becomes `--overlay`, selecting
+`overlays/<name>.yml` beside the root pipeline file. Remove `--profile` and old
+selected-directory discovery without aliases or fallbacks. Preserve existing
+base selection for omission, explicit empty selection, and `default`.
+Configuration inspection, diff descriptions, internal selection names, and
+newly written selection provenance use overlay terminology as well.
+
+Maintain existing value-based digest and stage-reuse semantics; renaming
+informational selection provenance is not a reason to invalidate completed
+work or rewrite historical manifests. Update maintained examples and operator
+migration guidance for the directory and flag changes.
+
+This rename does not apply to downstream model profiles, Scriptorium
+`profile_id`, Audita's proposal/validation profiles, or Notarius's
+`config_profile`. Nor does it prohibit ordinary explicit imports from a directory
+named `profiles`. Narratio overlays do not automatically select downstream
+overlays or profiles. These are independently owned choices.
+
+### Audita v2 configuration
+
 Keep binary, timeout, explicit config-path selection, and surviving explicit
 domain overrides such as transcript description, output schema, and modules.
 Allow Audita's native configuration discovery when no config path is selected;
@@ -81,7 +112,7 @@ do not impose an additional requirement to supply an explicit path.
 Provide optional Audita overlay, proposal-profile, and validation-profile
 selectors, passed through to their corresponding CLI flags. Omission leaves
 Audita's own defaults and validation-profile inheritance in control. These are
-Audita selectors, not automatic translations of Narratio profile names.
+Audita selectors, not automatic translations of Narratio overlay names.
 
 Retire the Narratio settings that mirror removed Audita endpoint/model/capacity
 flags and work-directory retention. Move their operational meaning into the
@@ -212,6 +243,10 @@ Update the canonical [configuration reference](../config.md),
 [polish internals](../internal/stage-polish.md), maintained examples, and relevant
 operations/troubleshooting guidance when implementation lands. Cover:
 
+- Moving selected Narratio pipeline files to `overlays/`, replacing `--profile`
+  with `--overlay`, and distinguishing configuration overlays from model profiles.
+- Updating ConfigKit API/source attribution and verifying unchanged effective
+  values retain existing semantic reuse behavior.
 - Preparing and validating an Audita v2 configuration and its profiles before
   switching the executable; copying an old v1 configuration is insufficient.
 - Moving endpoint, model, capacity, and credential selections to their v2 owners.