Add source-local version extraction

docs/roadmap/implementation.md

@@ -270,6 +270,23 @@ No environmental limitation affected validation; checks ran on Linux/amd64.
 Validate: helper/version-path/directive/inheritance-control tests and everyday
 check. Done: the processor is tested independently of public loading.
 
+Completion evidence: added a private source-local processor that resolves the
+configured path against the original document, separates imports, records
+private path/ancestor/location evidence, and consumes accepted contribution
+headers only from an owned payload copy. Missing and obstructed paths retain
+their cause and nearest available location; required absence fails before the
+checker, while optional main absence still invokes it. Structural directive
+overlap is rejected before payload consumption. Focused coverage includes the
+version vocabulary, malformed nodes, contextual numeric keys and indices,
+empty ancestors, sequence deletion, and actual versus unrelated structural
+overlap. These checks passed with Go `go1.26.8 linux/amd64`:
+
+- `GOTOOLCHAIN=local GOPROXY=off go test ./internal/engine -run 'SourceVersion|Version|Import|Underlay|Overlay|Destination|Inheritance'`
+- `GOTOOLCHAIN=local ./scripts/check.sh`
+- `git diff --check`
+
+No environmental limitation affected validation; checks ran on Linux/amd64.
+
 ## Stage 4 — Add private mode state and main-document integration
 
 1. Add the engine mode to ordinary/layered options and loadRequest. Validate it at