Share layered tier application

docs/internal/overview.md

@@ -101,7 +101,10 @@ source, filesystem, destination, and import settings.
 policy, load-wide accounting, and tier-scoped repetition/namespace state. Each
 input is acquired under that policy; grouped requests retain acquired underlay
 scopes until their tier is composed in
-[`load_request.go`](../../internal/engine/load_request.go). Live
+[`load_request.go`](../../internal/engine/load_request.go). Completed tiers then
+share one assembly handoff that applies collection declarations and projects
+only that tier's source/version evidence; the caller keeps main-version
+protection and its projection explicit. Live
 filesystem access handles are confined to acquisition and closed there. Resolved
 filesystem facts used to authorize access are separate from passively retained
 resource contexts. Non-import validation retains those facts on `assembledInput`

docs/roadmap/implementation.md

@@ -782,6 +782,13 @@ metadata/history/diff, and warnings remain stable. Update the implementation-flo
 description only after the handoffs actually land, without restating YAML policy.
 Focused check: `go test ./internal/engine -run 'Grouped|Layered|Underlay|SourceVersion|Sequence|Diff'`.
 
+Status: **complete** (completes F02). Prior completed F02 commits:
+`4bf940c`, `d8bf6ab`, `f185821`, and `a8ae2e9`. Validation passed:
+`env GOTOOLCHAIN=local GOPROXY=off GOTELEMETRY=off go test ./internal/engine -run 'Grouped|Layered|Underlay|SourceVersion|Sequence|Diff' -count=1`,
+`env GOTOOLCHAIN=local GOPROXY=off GOTELEMETRY=off go test ./internal/engine -count=1`,
+`env GOTOOLCHAIN=local GOPROXY=off GOTELEMETRY=off go test ./... -count=1`,
+and `git diff --check`.
+
 ## Stage 25 — Separate Collection Preparation, Application, And Finalization
 
 Finding: preparation/ownership part of **E03**.