fix: local-bridge robustness, scope-gate order, sentinel contract; packaging/docs closeout (P8-P11, P2/P3/P15)

Closes review #003 (prepublish review for v0.1.0).

- P8: StdinSink::poll_shutdown parks an inflight reserve+send on a
  full channel (waker registered) — a stdin blast followed by EOF
  delivers the EOF instead of stranding it
- P9: five poisoned-lock .expect() sites -> unwrap_or_else(into_inner)
- P10: three thread-spawn .expect() sites -> TtyError::AllocFailed
- P5: tty:open scope gate runs before carriage/cmd/backend-lookup
  checks (no backend-name enumeration differential for unscoped ids)
- P11: recv_stdout terminates on the zero-length drained sentinel;
  the sentinel is no longer yielded as an item (doc was already the
  contract); stderr has no sentinel (doc noted)
- P2: exclude AGENTS.md + docs/plans/, drop dead Cargo.lock and
  docs/research/ entries (package list: 42 files, 659.2KiB)
- P3: AGENTS.md phase status (all five landed), ADR range 001..009
  (+ alktty-native ADR-009 in the mapping), alkcall guidance
  corrected to v0.4.x / pin "0.4.0"; architecture README ADR-009 row
  + landed-phase status
- P15: backend.rs doc typo; redundant tokio-stream dev-dep removed;
  NegotiationError::Io arm logs; set_identity failure logs;
  input_pump.abort() at session end; TtySessionError::Open carries
  the accept_bi StreamError (no io::Error flattening); borrowing
  deserialize in open_via_channels (no params.clone());
  error_response_bytes guards an "error" key in fields; trivial
  inline comments promoted/removed; plan-doc test counts + doc
  front-matter refreshed; session tests that raced session teardown
  under the abort change use a GatedBackend (exit held until
  released)

Verification: cargo test 104 lib / --all-features 147; clippy
(all-targets + wasm32) -D warnings; fmt; wasm check; doc 0 warnings;
publish dry-run OK.

docs/architecture/README.md

@@ -19,7 +19,7 @@ Syntax Tree) document for the wire format, and the ADRs.
 ## Applicable ADRs
 
 Ported from the alknet mono-repo and renumbered into alktty's ADR
-range (001..008). The alknet originals at
+range (001..009; ADR-009 is alktty-native). The alknet originals at
 `/workspace/@alkdev/alknet/docs/architecture/decisions/` remain the
 authoritative source for any ADR not yet ported, and for the alknet
 ADRs referenced by alknet number in the docs below (which are not
@@ -35,6 +35,7 @@ tty-specific and therefore not ported into alktty's ADR range).
 | [006](decisions/006-negotiation-framing-self-contained.md) | Self-Contained Negotiation Framing (No alkcall-Internal-Wire-Types Dependency) | alknet ADR-057 | Accepted |
 | [007](decisions/007-tty-inside-channels.md) | TTY Inside Channels — Sub-Streams, Not Wire Format | alknet ADR-077 | Accepted (**reversed by ADR-008** — kept for historical context) |
 | [008](decisions/008-channels-pure-channel-multiplexing.md) | Channels Pure Channel Multiplexing (8-Byte Header, No `stream_type`) | alknet ADR-093 | Accepted (amends alknet ADR-071/074; reverses ADR-007) |
+| [009](decisions/009-channels-open-op-is-the-negotiation.md) | The Channels Open Op's `input` Is the Negotiation | alktty-native | Accepted (resolves review #001 L1; amended by review #002 R4 — parse failure is a client-visible error frame) |
 
 ## Key Design Principles
 
@@ -135,11 +136,10 @@ tty-specific and therefore not ported into alktty's ADR range).
 
 ## References
 
-- `docs/plans/project-setup.md` — the current plan (phases 0–5).
-  Phases 0–3 are landed; Phase 4 (this directory: architecture docs +
-  BAST schema + renumbered ADRs) is landed by this commit; Phase 5
-  (tests, including integration tests in `tests/` at the crate root) is
-  not yet done.
+- `docs/plans/project-setup.md` — the current plan (phases 0–5). All
+  five phases are landed: Phase 4 landed this directory (architecture
+  docs + BAST schema + renumbered ADRs); Phase 5 landed the tests,
+  including the integration tests in `tests/` at the crate root.
 - alknet originals of the ported ADRs (alknet ADR-052, 053, 054, 055,
   056, 057, 077, 093) at
   `/workspace/@alkdev/alknet/docs/architecture/decisions/` — the

docs/architecture/overview.md

@@ -2,8 +2,8 @@
 status: draft (ported from alknet 2026-08-17; alknet-tty → alktty,
   alknet-tty-local → alktty's `local` feature module, alknet/tty →
   alk/tty, alknet-core → alkcall::core, alknet-call → alkcall, ADRs
-  renumbered 052..093 → 001..008)
-last_updated: 2026-08-17
+  renumbered 052..093 → 001..009)
+last_updated: 2026-09-05
 ---
 
 # alktty — Overview

docs/architecture/tty-adapter.md

@@ -1,8 +1,8 @@
 ---
-status: draft (ported from alknet 2026-08-17; alknet-tty → alktty,
-  alknet/tty → alk/tty, alknet-core → alkcall::core, alknet-call →
-  alkcall, ADRs renumbered 052..093 → 001..008)
-last_updated: 2026-08-17
+status: draft (ported from alknet 2026-08-17; alknet/tty → alk/tty,
+  alknet-core → alkcall::core, alknet-call → alkcall, ADRs renumbered
+  052..093 → 001..009)
+last_updated: 2026-09-05
 ---
 
 # alktty — TtyAdapter and Session Lifecycle