Prepare sequence registration preflight

docs/roadmap/implementation.md

@@ -213,6 +213,24 @@ Scope: one ADR and engine option normalization; no new public fields yet.
 Validation: focused option tests and `./scripts/check.sh`. Completion: existing
 loads remain unchanged, with only private registered-policy input newly accepted.
 
+Completion evidence: added Accepted ADR 0014 and private engine registration
+normalization. Ordinary and layered entry points compile/coalesce policy and
+reject invalid registrations before source reads, then carry the compiled policy
+through the load request while clearing raw registration slices from internal
+handoffs. No public API or composition behavior was added. Focused coverage
+checks duplicate/conflicting definitions, empty identity names, numeric and
+escaped literal keys, invalid explicit indexes, unused/root registrations,
+zero-option behavior, and reader preservation on preflight failure. These checks
+passed with Go `go1.26.9 linux/amd64`:
+
+- `GOTOOLCHAIN=local GOPROXY=off go test ./internal/engine -run 'SequenceRegistration' -count=1`
+- `GOTOOLCHAIN=local ./scripts/check.sh`
+- `git diff --check`
+
+The compiled registration policy is intentionally not consumed by composition
+until the next implementation unit. No environmental limitation affected
+validation; checks ran on Linux/amd64.
+
 ## Stage 2 — Implement registered strict sequence validation and assembly
 
 Scope: `internal/engine/compose.go` and focused composition tests.