Check source versions in selected overlays

docs/roadmap/implementation.md

@@ -1,6 +1,6 @@
 # Implement shared source version checks
 
-Status: Stages 1–6 complete; selected overlay integration has not started.
+Status: Stages 1–7 complete; public load-wide mode integration has not started.
 
 Audience: a Luna coding agent implementing one numbered stage per prompt, in
 order. The [feature roadmap](source-version-checks.md) owns target behavior and
@@ -416,6 +416,27 @@ Validate: overlay/override/inheritance/version tests and everyday check. Done:
 all document roles are integrated privately; synthetic operations are exempt
 from header checks, not from existing protection.
 
+Completion evidence: threaded the shared version state through ordinary and
+layered selected-overlay loading. After parse and overlay-directive validation,
+the selected overlay is checked as a non-main source; accepted headers are
+removed from its owned payload before effective-path protection and application.
+The original parsed node still supplies raw byte/node charges, and source
+identity, filesystem namespace, closure, overlay-control checks, and override
+protection remain on their existing paths. Overlay warnings are accumulated with
+the other per-load diagnostics. Added coverage for accepted, required-missing,
+and rejected overlay declarations; structural validation before callbacks;
+warning retention; CLI overrides without document-header checks; mounted-main
+protection after header consumption; and sequence deletion retaining original
+evidence coordinates while later payload indices shift. Existing default overlay
+version/directive/accounting coverage remains passing. These checks passed with
+Go `go1.26.8 linux/amd64`:
+
+- `GOTOOLCHAIN=local GOPROXY=off go test ./internal/engine -run 'SourceVersion|Version|Import|Underlay|Overlay|Override|Inheritance|Destination' -count=1`
+- `GOTOOLCHAIN=local ./scripts/check.sh`
+- `git diff --check`
+
+No environmental limitation affected validation; checks ran on Linux/amd64.
+
 ## Stage 8 — Expose the public load-wide mode
 
 1. Add root mode/constants/option fields and both conversions from decision 1.