Project history and sensitivity paths

docs/roadmap/implementation.md

@@ -1,6 +1,6 @@
 # Implementation Plan: Sequence Placement and Composition
 
-Status: implementation in progress; stages 1–4 completed.
+Status: implementation in progress; stages 1–5 completed.
 
 ## Purpose and authority
 
@@ -372,6 +372,22 @@ Validation: metadata/provenance/history/explanation/secret tests,
 `go test -race ./internal/engine`, and `./scripts/check.sh`.
 Completion: the private registered composer can feed existing inspection safely.
 
+Completion evidence: history applications now expose one source-local/effective
+path traversal used by metadata enumeration, explanation replay, origin lookup,
+and secret classification. Appended records and nested descendants use assigned
+indexes while retained nodes and source locations remain local. Secret
+classification evaluates projected historical shapes before folding sensitivity
+by pointer, preserving numeric key/index distinctions and redacting replaced
+records. Tests cover shifted metadata/history/rendering, origin attribution, and
+redaction after replacement. These checks passed with Go `go1.26.9 linux/amd64`:
+
+- `GOTOOLCHAIN=local GOPROXY=off go test ./internal/engine -run 'Metadata|Provenance|History|Explain|Secret' -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 6 — Refactor acquisition into composition scopes without new behavior
 
 Scope: `imports.go`, `load_input.go`, `load_request.go`, and their handoffs.