docs(architecture): OQ-09 gains Option C — pure protocol crate (alktty template)

docs/architecture/open-questions.md

@@ -194,20 +194,36 @@ when their impacts say so; it records how careful the resolution must be.
   planned (after alksocks), alknet rewrite coming. Doors wrap alkcall
   producer/consumer in their wire protocol; services (git, tty, tunnels,
   socks) are payloads doors optionally expose. git should be a service
-  exposed by downstream consumers rather than owning its own doors:
-  candidate end-state is protocol crates (core + transport) + http adapter
-  either in alkgit or as an alkhttp `git` feature (Slim-B) or kept as
-  alkgit-http (Slim-A). alkssh is where git-over-ssh belongs when it
-  exists — the temporary russh-in-alkgitd decision (ssh.md) is scaffolding
-  either way.
+  exposed by downstream consumers rather than owning its own doors.
+  Candidate end-states: **Slim-A** — keep alkgit-http factory, 5-crate
+  layout, ADR-006 Option A as written; **Slim-B** — protocol crates +
+  alkhttp `git` feature for smart-http (requires alkgit published first);
+  **Option C (pure protocol crate)** — follow the alktty/alktunnels
+  template exactly: single `alkgit` crate, producer half (`GitAdapter`
+  for `alk/git` ALPN + channels `register_openable`, POC-1 substrate),
+  consumer half (typed `GitSession` — the replication/mirroring
+  primitive), backend traits (registry/refs/pack-gen/pack-ingest) with
+  the gix implementation feature-gated (mirrors alktty's `local`; NOT a
+  wasm goal, the cleanliness just falls out), smart-http stateless
+  substrate stays in-crate while the http mounting becomes alkhttp's
+  `git` feature. No binary; assembly is downstream's. Consequences to
+  record on commitment: vision.md's "single-binary git server" framing
+  is amended (assembly belongs to downstream consumers); ADR-001/006
+  superseded by a new ADR; ssh.md defers entirely to alkssh (the
+  temporary russh scaffolding decision is dropped, not shipped); OQ-08
+  narrows to the registry identity space + vault placement.
 - **Sub-decisions**: (1) delete `alkgit-ssh` now and defer git-over-ssh to
   alkssh, or keep temporary russh scaffolding in alkgitd until then
   (hinges on whether our deployment needs git-over-ssh before alkssh
   lands); (2) http adapter home — Slim-A (keep alkgit-http, ADR-006
   Option A as written) vs Slim-B (alkhttp 0.6 `git` feature; requires
-  alkgit published first); (3) if Slim-B, whether `alkgitd` keeps an
-  internal factory consumption path or consumes the alkhttp feature like
-  any downstream.
+  alkgit published first); (3) crate granularity — keep core+transport
+  split (embedders wanting storage-only) vs merge into one `alkgit`
+  (Option C's shape); (4) under Option C, backend-trait surface: full
+  family (registry, refs, pack-gen, pack-ingest) vs minimal (pack +
+  registry, refs ride the registry trait); (5) alkgitd's fate — deleted,
+  or kept as a thin reference assembly once doors exist to assemble
+  against.
 - **Resolution path**: dedicated discussion session; decide the three
   sub-decisions, then rewrite ADR-001/006 and ssh.md (a new ADR superseding
   the affected parts, per ADR stability rules), and re-scope OQ-08.