docs(reviews): post-remediation re-review — gate passed, specs to reviewed

- docs/reviews/002-post-remediation-review.md: verifies all 14 review-001
  findings landed faithfully (sibling-source re-verification + gix-transport
  async_trait(?Send) check + four-config/MSRV probes), records the eight
  residual findings (R-1..R-8) and their resolutions (ADR-018 + doc batch)
- README lifecycle: draft→reviewed allows properly-tracked non-circular
  OQ deferrals (release-timing OQ-03 no longer blocks the transition) — R-7
- overview/transport/backend/doors/open-questions: frontmatter flipped to
  reviewed, timestamps refreshed; ADR-018 added to all ADR tables and the
  OQ-03 freeze-inventory narrative

Phase-1 gate verdict: decomposition may begin
Verification: cargo doc/test/clippy/fmt clean; four feature configs +
MSRV 1.88 check/clippy clean

docs/architecture/open-questions.md

@@ -1,6 +1,6 @@
 ---
-status: draft
-last_updated: 2026-09-25
+status: reviewed
+last_updated: 2026-09-30
 ---
 
 # Open Questions
@@ -75,7 +75,11 @@ resolved in earlier cycles. OQ-16 is deferred but blocks nothing in v1
   grammar — the last native-path wire surface); ADR-017 added the
   `GitSession` public API; the registry types/schemas draft
   (backend.md §"Registry types and schemas", review 001 N-3) pinned
-  `RepoRecord`, `RegistryError`, and the `git/repo/*` op schemas.
+  `RepoRecord`, `RegistryError`, and the `git/repo/*` op schemas;
+  ADR-018 pinned the object-storage trait signatures, the shared
+  backend-seam types (`RefLine`/`RefUpdate`/`RefOutcome`/
+  `PreparedPush`/`PushOptions`), and `StorageError` — the backend-seam
+  inventory is complete.
 - **Door type**: one-way (API freeze is registry-visible to dependents)
 - **Priority**: medium
 - **Impacts**: blocks the first publish only, not implementation.
@@ -86,7 +90,7 @@ resolved in earlier cycles. OQ-16 is deferred but blocks nothing in v1
   (`GitPackIngest` binding, `GitPackGen::common_haves`) to the freeze
   inventory; ADR-016 added the native preamble wire shapes.
 - **Cross-references**: ADR-010, ADR-002, ADR-012, ADR-013, ADR-014,
-  ADR-016, backend.md, transport.md
+  ADR-016, ADR-018, backend.md, transport.md
 
 ## Theme: transport / protocol