Separate explanation replay snapshots and rendering

docs/internal/overview.md

@@ -51,9 +51,11 @@ module and package documentation boundary. Its implemented public primitives are
   `secrets.go`;
 - fixed-point tag/predicate/dependency sensitivity classification in `secret.go`;
 - frozen-snapshot redaction and canonical effective output in `render.go`;
-- bounded immutable input applications, safe historical replay, detached explanation
-  records, and deterministic human rendering in `explain.go`, with the
-  only upstream dumper integration isolated in `internal/yaml/write.go`;
+- detached public explanation records and coordination in `explain.go`, immutable
+  input applications/replay and retained-node budgeting in `history.go`, shared
+  safe snapshot projection in `snapshot.go`, and deterministic human output in
+  `explain_render.go`; the only upstream dumper integration remains isolated in
+  `internal/yaml/write.go`;
 - a separate maintained `examples/consumers` package with four sanitized consumer
   shapes, fixtures, domain validators, and runtime-boundary functions; and
 - a fail-fast source-candidate checker in `scripts/release-check.sh`, with local

docs/roadmap/remediation.md

@@ -338,7 +338,16 @@ ordering by reading the coordinator. Run the complete race suite.
 
 ## Stage 8 — Separate explanation replay, snapshots, and rendering
 
-Status: pending.
+Status: complete.
+
+Completion: public records and Explain coordination remain in `explain.go`;
+immutable applications, replay/coalescing, and shared-node budgeting live in
+`history.go`; shared effective/explanation redaction lives in `snapshot.go`;
+human output lives in `explain_render.go`. Metadata versus replay ownership is
+documented beside history. Existing reconciliation, historical sensitivity,
+container/leaf, retained-budget, detachment, and writer-failure tests passed
+without expectation changes. Full offline tests, vet, build, and whitespace
+checks passed with Go 1.26.7 on Linux/amd64.
 
 Evidence: [explain.go](../../explain.go) combines approximately 576 lines of public
 records, replay algorithms, snapshot redaction, retained-history accounting, and