phase 5: port integration tests (negotiation, pipe, pty)

Port the integration test suite from alknet-tty-local/tests/ into
tests/ at the crate root, plus the shared ClientSide harness. The
inline unit tests (wire, negotiation, control, adapter, session,
channels) were already ported in Phases 1-2 alongside the production
code; this completes Phase 5 step 2 (integration tests) — Phase 5
step 3 (channels integration tests) landed inline in src/channels.rs
mod tests in Phase 2.

Tests:
- tests/common/mod.rs — ClientSide wire-protocol harness +
  spawn_session helper + negotiate_pty_json / negotiate_pipe_json
  builders. Imports renamed alknet_core::auth::Identity ->
  alkcall::core::auth::Identity, alknet_tty::... -> alktty::...
- tests/negotiation.rs — 4 negotiation-error scenarios
  (unknown_backend, malformed_negotiation x3, allocate_failed)
- tests/pipe.rs — 6 pipe-mode scenarios (echo, separate stderr,
  SIGTERM, cancel cleanup, resize no-op, stdout sentinel). The 2
  cancel-cleanup / SIGTERM tests are #[cfg(unix)].
- tests/pty.rs — 8 PTY-mode scenarios (echo, interactive cat,
  resize, SIGINT, process-group signal, stdin-EOF sentinel,
  cancel cleanup, exit-chunk-is-last). The 4 signal /
  cancel-cleanup tests are #[cfg(unix)].

Each test file carries #![cfg(feature = "local")] so the default
crate (no features) skips the integration binaries and stays
wasm-buildable. The pty/pipe cancel-cleanup tests use
unsafe { libc::kill(pid, 0) } to probe the child — matching the
existing pattern in src/local/ (libc::kill is a safe libc crate
API wrapped in an unsafe block per Rust's foreign-function rules;
no new in-crate unsafe beyond what src/local/ already has).

Plan doc updated: Phase 5 marked landed 2026-08-17.

Verification:
- cargo test                         -> 80 lib tests pass
- cargo test --all-features          -> 99 tests pass (80 lib +
  5 negotiation + 6 pipe + 8 pty)
- cargo clippy --all-targets --all-features -- -D warnings -> clean
- cargo clippy --target wasm32-unknown-unknown -- -D warnings -> clean
- cargo fmt --check                  -> clean

docs/plans/project-setup.md

@@ -2,7 +2,7 @@
 
 Status: draft (revised 2026-08-17 to reflect landed upstream changes;
 Phase 4 landed 2026-08-17 — architecture docs + BAST schema +
-renumbered ADRs)
+renumbered ADRs; Phase 5 landed 2026-08-17 — tests)
 Last updated: 2026-08-17
 
 ## Overview
@@ -488,18 +488,47 @@ split (`STREAM_CTRL_IN` = 3, `STREAM_CTRL_OUT` = 4) is an amendment
 inside ADR-001, mirroring alknet (it was not a standalone ADR there
 either). `AGENTS.md` was updated to match this mapping.
 
-### Phase 5: Tests
+### Phase 5: Tests — landed 2026-08-17
 
-1. Port existing unit tests from `alknet-tty` (wire, negotiation,
-   control, adapter) — these live inline in each `src/*.rs` module's
-   `#[cfg(test)] mod tests`.
-2. Port integration tests from `alknet-tty-local/tests/` (negotiation,
-   pipe, pty) into `tests/` at the crate root. The pty test stays
-   `#[cfg(unix)]`.
-3. Add channels integration tests — end-to-end `register_openable` +
-   `ChannelClient::open_channel` + `drive_session` round-trip. Use
-   the in-memory `MockBackend` from `backend.rs` for the producer
-   side so the test doesn't need a real PTY.
+1. Ported existing unit tests from `alknet-tty` (wire, negotiation,
+   control, adapter) inline in each `src/*.rs` module's
+   `#[cfg(test)] mod tests` — done in Phases 1–2 alongside the
+   production code (80 lib tests, all passing).
+2. Ported integration tests from `alknet-tty-local/tests/` into
+   `tests/` at the crate root:
+   - [`tests/common/mod.rs`](../tests/common/mod.rs) — the
+     `ClientSide` wire-protocol harness + `spawn_session` helper +
+     `negotiate_pty_json` / `negotiate_pipe_json` builders. Imports
+     renamed `alknet_core::auth::Identity` →
+     `alkcall::core::auth::Identity`, `alknet_tty::...` →
+     `alktty::...`.
+   - [`tests/negotiation.rs`](../tests/negotiation.rs) — 4
+     negotiation-error scenarios (unknown_backend,
+     malformed_negotiation ×3, allocate_failed).
+   - [`tests/pipe.rs`](../tests/pipe.rs) — 6 pipe-mode scenarios
+     (echo happy path, separate stderr, SIGTERM, cancel cleanup,
+     resize no-op, stdout sentinel). The 2 cancel-cleanup /
+     SIGTERM tests are `#[cfg(unix)]`.
+   - [`tests/pty.rs`](../tests/pty.rs) — 8 PTY-mode scenarios
+     (echo, interactive cat, resize, SIGINT, process-group
+     signal, stdin-EOF sentinel, cancel cleanup,
+     exit-chunk-is-last). The 4 signal / cancel-cleanup tests
+     are `#[cfg(unix)]`.
+   Each test file carries `#![cfg(feature = "local")]` so the
+   default crate (no features) skips the integration binaries
+   and stays wasm-buildable; `cargo test --all-features` runs
+   all 19 integration tests (5 + 6 + 8).
+3. Added channels integration tests inline in
+   [`src/channels.rs`](../src/channels.rs) `mod tests` (done in
+   Phase 2 alongside the producer code): `register_openable`
+   registration, end-to-end `ChannelClient::call_open_op` returns
+   `channel_id`, scope-gate denies without `tty:open`, and the
+   `MockBackend` exit-code sanity check. Uses the in-memory
+   `MockBackend` from `backend.rs` for the producer side so no
+   real PTY is needed.
+
+Total: 80 lib tests + 19 integration tests = 99 passing under
+`--all-features`; 80 lib tests under default (wasm-clean) build.
 
 ## Open Questions