docs(architecture): N-4 + N-5 — push-options trait param, unborn-HEAD rider

- N-4: GitPackIngest's prepare binding carries push_options:
  Option<&PushOptions> (parsed (key, value) pairs, verbatim and
  un-interpreted; None until the config gate opens) — pinned in
  ADR-013 §11 and backend.md's trait description so opening the
  config gate later is value-additive, not a trait redesign
- N-5: ls-refs=unborn verification recorded as a rider in
  transport.md §ls-refs + tracker task tasks/architecture/
  n5-unborn-head-rider.md (unborn fixture, real client, both
  substrates; drop the token if it cannot be served — ADR-003)
- review 001: N-4, N-5 marked resolved

verification: cargo test, clippy -D warnings, fmt --check, doc — clean

docs/reviews/001-architecture-pre-decomposition-review.md

@@ -770,8 +770,8 @@ criticals are ADR-writing work, not code):
 | N-1 | ref-cap breach behavior | one fail-closed clause in transport.md | trivial | none | **resolved** — ref cap fail-closed clause in transport.md §Limits (breach is an error, never truncation) |
 | N-2 | unknown ≡ unauthorized at wire mapping | one sentence in transport.md error taxonomy | trivial | none | **resolved** — collapse rule stated at the variant→wire mapping in transport.md §error taxonomy |
 | N-3 | schemas unpinned | backend.md types/schemas section | small | freeze inventory | open |
-| N-4 | push-options seam | pin additive parameter shape | trivial | none | open |
-| N-5 | `ls-refs=unborn` unverified | implementation-phase test rider (record in transport.md or a task) | trivial | none | open |
+| N-4 | push-options seam | pin additive parameter shape | trivial | none | **resolved** — `GitPackIngest`'s prepare binding carries `push_options: Option<&PushOptions>` (parsed `(key, value)` pairs, verbatim and un-interpreted; `None` until the config gate opens) — pinned in ADR-013 §11 + backend.md trait description, so opening the gate is value-additive, not a trait redesign |
+| N-5 | `ls-refs=unborn` unverified | implementation-phase test rider (record in transport.md or a task) | trivial | none | **resolved (rider)** — unborn-HEAD verification recorded in transport.md §ls-refs and tracker task `tasks/architecture/n5-unborn-head-rider.md` (unborn fixture, real client, both substrates; drop the token if it cannot be served — ADR-003) |
 
 Suggested sequencing: (1) **A-2 + A-6** together (one trait-surface
 amendment set + manifest change — they are the same signature surface);