Integrate source version checks for main inputs

docs/roadmap/implementation.md

@@ -1,6 +1,6 @@
 # Implement shared source version checks
 
-Status: Stages 1–2 complete; source-local extraction has not started.
+Status: Stages 1–4 complete; recursive import 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
@@ -305,6 +305,26 @@ No environmental limitation affected validation; checks ran on Linux/amd64.
 Validate: load/grouped/version/destination/hook tests and everyday check. Done:
 private enabled main behavior works without changing old callers.
 
+Completion evidence: added the private mode to ordinary and layered engine
+options and the shared load request. Both entry points validate enabled modes
+and their shared checker before source acquisition; enabled loads build schema
+before invoking the main checker. The parsed main document is checked at its
+source-local path before import traversal or layered composition, and its node
+remains in the application payload. A single semantic destination-prefixed rule
+now protects mounted main ownership during decoding, inheritance, acquired-input
+placement, overlays, and CLI overrides; declaration callbacks and diagnostics
+retain local paths. Default mode keeps its prior post-composition check timing.
+The per-load assembled input retains main evidence and successful warning
+diagnostics. NoSource invokes the existing absent-main callback once in either
+enabled mode. These checks passed with Go `go1.26.8 linux/amd64`:
+
+- `GOTOOLCHAIN=local GOPROXY=off go test ./internal/engine -run 'SourceVersion|Version|Load|Grouped|Destination|Hook'`
+- `GOTOOLCHAIN=local ./scripts/check.sh`
+- `git diff --check`
+
+No environmental limitation affected validation; checks ran on Linux/amd64.
+The engine mode remains private; public options are scheduled separately.
+
 ## Stage 5 — Integrate recursive imports, warnings, and accounting
 
 1. Thread shared state through import entry/traversal. Check each acquired child