Separate version interpretation from reporting

docs/roadmap/implementation.md

@@ -1,6 +1,6 @@
 # Implement shared source version checks
 
-Status: Stage 1 complete; runtime implementation has not started.
+Status: Stages 1–2 complete; source-local extraction 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
@@ -241,6 +241,20 @@ were made.
 Validate: engine version/validation and facade version tests; everyday check.
 Done: shared mechanisms exist with unchanged default behavior.
 
+Completion evidence: `checkVersion` remains the existing diagnostic-only entry
+point and now delegates to private scalar interpretation and callback-reporting
+helpers through a result that keeps the interpreted `Version` separate from
+diagnostics. Checker invocation and returned-error fallback use diagnostic
+severity, preserving warnings without treating them as failures. Added a
+regression for a warning followed by a returned checker error. These checks
+passed with Go `go1.26.8 linux/amd64`:
+
+- `GOTOOLCHAIN=local GOPROXY=off go test ./internal/engine -run 'Version|Validation'`
+- `GOTOOLCHAIN=local GOPROXY=off go test . -run 'Version'`
+- `GOTOOLCHAIN=local ./scripts/check.sh`
+
+No environmental limitation affected validation; checks ran on Linux/amd64.
+
 ## Stage 3 — Implement source-local extraction and exact consumption
 
 1. Add a private processor receiving original document, local rule, source role,