Project version protections through item placement

docs/roadmap/implementation.md

@@ -1,6 +1,6 @@
 # Implementation Plan: Sequence Placement and Composition
 
-Status: implementation in progress; stages 1–9 completed.
+Status: implementation in progress; stages 1–10 completed.
 
 ## Purpose and authority
 
@@ -595,6 +595,22 @@ Validation: source-version/version/inheritance/override/resolution tests,
 `go test -race ./internal/engine`, and `./scripts/check.sh`.
 Completion: item placement changes coordinates, not version or structural policy.
 
+Completion evidence: enabled source-version rules now derive their effective
+paths through the main item's assigned index, while default-mode coordinates
+remain unchanged. Structural import and underlay checks use assigned sequence
+ranges so they protect the actual main item without rejecting unrelated peers;
+source-local checking still runs once per original source, and projected header
+evidence is used for sensitivity. Tests cover ordinary and layered placement,
+protected versus peer indexes, nested projections, and redacted version
+evidence. These checks passed with Go `go1.26.9 linux/amd64`:
+
+- `GOTOOLCHAIN=local GOPROXY=off go test ./internal/engine -run 'SourceVersion|Version|Inheritance|Override|Resolution' -count=1`
+- `GOTOOLCHAIN=local GOPROXY=off go test -race ./internal/engine`
+- `GOTOOLCHAIN=local ./scripts/check.sh`
+- `git diff --check`
+
+No environmental limitation affected validation; checks ran on Linux/amd64.
+
 ## Stage 11 — Expose root-owned controls and detached placement evidence
 
 Scope: root facade declarations, conversions, and public integration tests.