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  thin-wrapper reading is superseded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  gix-protocol call — resolved; rider superseded); backend/transport/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/architecture/overview.md

@@ -30,7 +30,7 @@ Single crate `alkgit`:
 | Half | Contents | POC evidence |
 |---|---|---|
 | Producer | `GitAdapter` (`alk/git` ALPN via alkcall `ProtocolHandler`; parses the ADR-016 request-line preamble), channels `register_openable` (`channels/git/sub` — open-op params `{repo, service}`, the negotiation + service selector + ACL point; ADR-016) | POC-1 verbatim |
-| Consumer | `GitSession` typed client (`connect_direct`, `open_via_channels`) — sends the same ADR-016 preamble shapes | new, small (TtySession analog) |
+| Consumer | `GitSession` typed client (`connect_direct`, `open_via_channels`) — ADR-017: `ls_refs`/`fetch`/`push`; fetch via gitoxide client machinery over a custom alkcall Transport, push hand-rolled to ADR-013's shapes; the replication/mirroring primitive for alknet | new, specified (grammar capture-grounded: ADR-013/014 + captures) |
 | Substrate | duplex session + stateless request/response layer (ADR-005); wire framing, V2 state machines (ADR-003) | POC-1, POC-3 |
 | Backends | `GitRegistry` (+ write supertrait), `GitRefs`, `GitPackGen`, `GitPackIngest` traits; impls behind the default-on `gix` (engine) and `registry-file` (records) features | POC-2 (gix impl) |
 | Management ops | `git/repo/*` call ops over `GitRegistryStore` (ADR-012 §3) — the JSON half alongside the `alk/git` open op (first dual-kind payload; ADR-012 §5) | thin over the store trait |
@@ -94,6 +94,7 @@ multi-round negotiation are design-complete against real-client captures
 | [014](decisions/014-v2-negotiation-ack-loop.md) | Negotiation | ack loop, `common_haves` seam, no `ready` |
 | [015](decisions/015-manage-grant-and-op-gate.md) | Manage grant + op gate | `manage` tier, admin-OR-manage gate, create seeds manage |
 | [016](decisions/016-native-session-preamble.md) | Native session preamble | `{repo, service}` open-op params, request-line preamble, service in the tuple |
+| [017](decisions/017-consumer-half-git-session.md) | Consumer half | `GitSession` typed client, custom alkcall Transport + gix-protocol fetch, hand-rolled push |
 
 ## Open Questions
 
@@ -103,7 +104,8 @@ Key questions tracked in [open-questions.md](open-questions.md):
   and the trait family enter it; ADR-012, ADR-013/014's trait additions;
   the ADR-015 three-action grant shape must land in it; the ADR-016
   native preamble wire shapes — `{repo, service}` params schema and the
-  request-line grammar — entered it).
+  request-line grammar — entered it; ADR-017's `GitSession` public API
+  enters it).
 - **OQ-05**: sha256 policy (deferred(scope), low).
 - **OQ-16**: grant-key identity namespace (deferred(scope); blocks
   nothing in v1 — ADR-015 §7).