docs(architecture): ADR-017 — consumer half, GitSession as typed client (review 001 A-5)

- new ADR-017: GitSession is a real typed client in v1 (ls_refs/fetch/
  push), grounded in the two deployment use cases — the p2p replicator
  is the named downstream and needs the client protocol layer; the
  thin-wrapper reading is superseded
- fetch client reuses gix-protocol (async-client) over a custom
  alkcall gix_transport::client::Transport impl (handshake writes the
  ADR-016 request line on the direct path; the channels open-op params
  carry it otherwise); push hand-rolled to ADR-013's shapes (gitoxide
  has no send-pack client)
- storage-agnostic: packs stream both ways to caller-owned consumers;
  no in-session credentials (alkcall transport authenticates); client
  sessions carry ADR-009 Limits (client is also internet-facing)
- manifest: gix-protocol/gix-transport gain async-client features
  (verified against published tree, MSRV 1.88)
- amend ADR-010 (consumer-half bullet) and ADR-012 §4 (the deferred
  gix-protocol call — resolved; rider superseded); backend/transport/
  overview/doors wording; review 001 A-5 marked resolved

verification: cargo check (default, --all-features, --no-default-features,
--features sha256), cargo +1.88 check, cargo test, clippy
-D warnings, fmt --check — clean across the matrix

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

@@ -762,7 +762,7 @@ criticals are ADR-writing work, not code):
 | A-2 | `async fn` traits not dyn-compatible | ADR-012 §1 + backend.md amendment: `#[async_trait]`; add `async-trait = "0.1"` to manifest | small | none | **resolved** — all five traits `#[async_trait]`, desugared boxed form pinned in the freeze inventory (OQ-03), dep in manifest |
 | A-3 | native preamble / service dimension unpinned | new ADR: open-op params `{repo, service}`, session tuple + stateless entry gain the service selector, `GitAdapter` preamble pinned | moderate | wire-format (freeze inventory) | **resolved (ADR-016)** — `{repo, service}` open-op params (`channels/git/sub`, `additionalProperties: false`), git-daemon request line on the direct path (POC-1 verbatim, freeze inventory), service in both substrate tuples, `GitSession` mirrors the shapes |
 | A-4 | done-round boundary set unverified | ADR-014 §2 + transport.md clause: boundary = `common_haves`-filtered haves | trivial | none | **resolved** — boundary set is the recognized subset (`common_haves`-filtered), amendment clause in ADR-014 §2 + transport.md §fetch |
-| A-5 | consumer half unspecified | user scope decision, then amendment or small ADR (recommended: thin wrapper, deps carried with purpose) | small | scope | open |
+| A-5 | consumer half unspecified | user scope decision, then amendment or small ADR (recommended: thin wrapper, deps carried with purpose) | small | scope | **resolved (ADR-017)** — superseding the thin-wrapper recommendation: `GitSession` is a real typed client in v1 (`ls_refs`/`fetch`/`push`), grounded in the two deployment use cases (the p2p replicator is the named downstream and needs the client protocol layer); fetch reuses gix-protocol over a custom alkcall `Transport`, push is hand-rolled to ADR-013's shapes (gitoxide has no send-pack), storage-agnostic |
 | A-6 | trait execution model unspecified | backend.md paragraph + transport.md rephrase: async traits, wire-layer permit, impl-internal spawn_blocking | small | none | **resolved** — backend.md concurrency model: wire layer enforces the ADR-009 permit around gen/ingest trait calls; impls own internal `spawn_blocking` (ADR-009/ADR-013 aligned) |
 | D-1 | stale Internal-ops + OQ-list text | supersession notes (vision, alk-stack, AGENTS) | trivial | none | **resolved** — supersession notes in vision.md (with ADR-015) and alk-stack.md item 2; AGENTS.md active-OQ list updated to OQ-03/05/16 |
 | D-2 | ADR-007 step-3 mechanism superseded | amendment note on ADR-007 | trivial | none | **resolved** — amendment note on ADR-007 step 3 (mechanism → ADR-011 `authorize`; step order unchanged) |