Project sequence origins onto appended indexes

docs/roadmap/implementation.md

@@ -291,6 +291,21 @@ Scope: composition evidence, not import acquisition.
 Validation: composition/provenance/path tests and `./scripts/check.sh`.
 Completion: correct trees and effective origins share the same record ordering.
 
+Completion evidence: composition origins now traverse each source document with
+separate local and effective semantic paths. Stage 2's source ranges shift list
+items and descendants to assigned indexes while retaining each field's physical
+location and contributor order at sequence containers; conflict claims remain
+source-local. Tests cover a later source's local index zero becoming effective
+index one, mounted and escaped/numeric-key paths, multiple collections, and
+detached origins, claims, ranges, and input trees. These checks passed with Go
+`go1.26.9 linux/amd64`:
+
+- `GOTOOLCHAIN=local GOPROXY=off go test ./internal/engine -run 'Compose|Provenance|Path' -count=1`
+- `GOTOOLCHAIN=local ./scripts/check.sh`
+- `git diff --check`
+
+No environmental limitation affected validation; checks ran on Linux/amd64.
+
 ## Stage 4 — Preserve append history and whole-list tier replacement
 
 Scope: private history operations, replay, and precedence handoff.