feat: allocation moves into the channels establisher (alkcall 0.6.0 / review 007 R-01) — bump to 0.3.0

- Bump alkcall 0.5.0 -> 0.6.0 (Establishment plan payload, ADR-049
  amendment 2); alktty 0.2.0 -> 0.3.0 (breaking channels-path
  allocation-failure shape)
- make_tty_establisher runs backend.allocate; failure maps to
  EstablishmentError::DialFailed (channel:open_failed reason
  dial_failed); the TtyHandle crosses to the pump handler via a
  private per-open AllocatedHandle one-shot slot (the handle is not
  Sync — it cannot be the ChannelPlan directly)
- make_tty_open_handler gains the Option<ChannelPlan> parameter; a
  plan drives the new drive_session_pre_allocated (pumps only), a
  None plan falls back to drive_session_pre_negotiated (inline
  validate-and-allocate — defense-in-depth for no-establisher
  registrations)
- tty_open_spec's channel:open_failed ErrorDefinition declares
  dial_failed (four reachable reasons)
- Pinned in-band allocate test flipped:
  allocate_failure_fails_open_as_dial_failed (end-to-end, no channel
  survives); establisher unit gate for the plan slot + failure
  mapping
- ADR-010 amended (§2A; §2 kept as historical record), tty-adapter.md,
  session/channels/adapter docs, CHANGELOG, AGENTS.md alkcall pin
  updated

Verification: cargo test (113) + --all-features (137), clippy
-D warnings (native + wasm32, default + all-features), fmt, doc,
wasm32 check — all clean

docs/architecture/decisions/010-channels-establisher-migration.md

@@ -10,6 +10,19 @@ error frame is retained — two transports, two contracts").
 Prerequisites: alkcall 0.5.0 (`ChannelCore::register_openable_with_establisher`,
 `channel:open_failed`, typed `ChannelOpenError`).
 
+**Amended (2026-09-07, alkcall 0.6.0 / ADR-049 amendment 2 — review
+007 R-01):** `Establishment` gained its plan payload
+(`ChannelPlan = Arc<dyn Any + Send + Sync>`), removing §2's
+payloadless-`Establishment` blocker. Backend `allocate` moves into
+the establisher; the allocated `TtyHandle` crosses to the pump
+handler via the plan; `allocate_failed` joins the call-error surface
+as `details.reason == "dial_failed"` (the target refused or the
+backend lacked capacity). No failure class arrives in-band on the
+channels path from a registered producer; the in-band error-frame
+fallback stays for no-establisher registrations (defense-in-depth)
+and the direct-ALPN path. See §2A below; §2 is retained as
+historical record.
+
 Amends ADR-009's R4 amendment: the in-band error-frame path on the
 channels path shrinks to one failure class (`allocate_failed`).
 
@@ -68,18 +81,26 @@ the vocabulary is alkcall's one-way wire surface):
 | `carriage != "raw"`, empty `cmd` | `HandlerError` | `handler_error` |
 | unknown backend | `UnknownResource` | `unknown_resource` |
 | ownership denial | `HandlerError` | `handler_error` |
+| **allocation failure** (amended — §2A) | `DialFailed` | `dial_failed` |
 | establishment deadline | (wrapper) | `timeout` |
 
-`dial_failed` and `resource_shortage` have no TTY producer path (TTY
-dials nothing at open time; `allocate` capacity failures are the
-in-band class below) — the spec's `ErrorDefinition` for
-`channel:open_failed` declares only the three reachable reasons.
-`HandlerError` covers both the malformed-negotiation semantics (the
-request shape is wrong) and the ACL-outcome ownership denial (an
-authorization failure, not a dial failure).
+`resource_shortage` has no TTY producer path (allocation-capacity
+failures map to `dial_failed` — the target refused or the backend
+lacked capacity; §2A). `HandlerError` covers both the
+malformed-negotiation semantics (the request shape is wrong) and the
+ACL-outcome ownership denial (an authorization failure, not a dial
+failure).
 
 ### 2. Backend allocation stays in the pump handler — `allocate_failed` stays in-band
 
+> **Amended away (2026-09-07) — see §2A.** This section is the
+> historical record of the pre-0.3.0 shape; its blocker 1
+> (payloadless `Establishment`) was resolved by alkcall 0.6.0 (ADR-049
+> amendment 2, review 007 R-01). Blocker 2 (double-`allocate`
+> unsoundness) is avoided by construction in the amended shape: the
+> establisher's handle *is* the handle the handler pumps — there is no
+> second allocate to be unsound about.
+
 The one failure class that cannot migrate: `backend.allocate`. Two
 reasons, both structural:
 
@@ -114,6 +135,60 @@ no-establisher registration still compiles against alkcall's API and
 must not silently EOF), and the R4 seam test pins the handler-side
 frame.
 
+### 2A. Amendment (alkcall 0.6.0): allocation moves into the establisher
+
+alkcall 0.6.0 (ADR-049 amendment 2, review 007 R-01) filled the
+reserved field: `Establishment { plan: Option<ChannelPlan> }` with
+`ChannelPlan = Arc<dyn Any + Send + Sync>` — typed-opaque, wrapper
+threaded to the `OpenHandler`'s new second parameter. §2's blocker 1
+is gone; the double-`allocate` hazard (blocker 2) is structurally
+absent — one allocate per open, whose result the handler consumes.
+
+The amended shape:
+
+1. **The establisher allocates.** After the validation sequence (§1),
+   it runs `backend.allocate(&params)`. Failure maps to
+   `EstablishmentError::DialFailed` (`details.reason == "dial_failed"`
+   — the target refused or the backend lacked capacity; one string
+   message, no nuance — the same granularity the direct path's
+   `allocate_failed` frame always had). The
+   `channel:open_failed` `ErrorDefinition` on `tty_open_spec()`
+   therefore declares four reachable reasons (`dial_failed`,
+   `unknown_resource`, `handler_error`, `timeout`).
+2. **The handle crosses via the plan.** `TtyHandle` is not `Sync`
+   (boxed dyn streams), so it cannot be the `ChannelPlan` directly.
+   The establisher wraps it in a private `AllocatedHandle` one-shot
+   slot (`Mutex<Option<TtyHandle>>`), created **per establisher
+   invocation** — per open. The wrapper moves this open's plan to this
+   open's handler (alkcall's concurrent-same-resource test pins that
+   plans are never shared), the handler `take()`s it exactly once, and
+   establisher-before-handler ordering is alkcall's wrapper guarantee
+   (ADR-049 §1). The shared-slot race §2 described is unreachable by
+   construction: there is no shared slot.
+3. **The handler pumps the pre-allocated handle.** With a plan it
+   calls `drive_session_pre_allocated` (new `pub(crate)` driver: the
+   pumps directly, no validation pass). With `plan: None` — a
+   no-establisher registration — it falls back to
+   `drive_session_pre_negotiated`, whose inline validate-and-allocate
+   keeps the full in-band error-frame vocabulary. That fallback is
+   defense-in-depth for the assembly-layer freedom to register without
+   an establisher, not a registered-producer path.
+4. **Consumer surface.** `TtySession::open_via_channels` sees
+   allocation failure as
+   `ChannelsOpen(CallFailed{ channel:open_failed, reason:
+   dial_failed })` — a typed call error, branchable and retryable
+   like every other establishment class. The `0x00` peek on the
+   channel stream becomes a formality that no registered producer
+   ever exercises; the pinned test flipped with the contract
+   (`allocate_failure_fails_open_as_dial_failed` in `testing.rs`,
+   plus the establisher unit gate `establisher_allocates_and_maps_
+   failure_to_dial_failed` in `channels.rs`).
+
+The R-02 lifetime contract (the handler's `JoinHandle` tracks the
+data-plane lifetime) was already alktty's shape — the open handler
+awaits the driver inline in its spawned task — so the amendment adds
+no lifetime changes.
+
 ### 3. The direct-ALPN path is unchanged
 
 `TtyAdapter::handle` / `drive_session` keep the wire-frame
@@ -149,10 +224,10 @@ unchanged (`true` direct, `false` channels — the registry's
 | malformed negotiation (schema-valid) | establisher | `ChannelsOpen(CallFailed{ channel:open_failed, reason: handler_error })` |
 | unknown backend | establisher | `ChannelsOpen(CallFailed{ channel:open_failed, reason: unknown_resource })` |
 | ownership denial | establisher | `ChannelsOpen(CallFailed{ channel:open_failed, reason: handler_error })` |
+| **allocation failure** (amended — §2A) | establisher | **`ChannelsOpen(CallFailed{ channel:open_failed, reason: dial_failed })`** |
 | establishment timeout | wrapper bound | `ChannelsOpen(CallFailed{ channel:open_failed, reason: timeout })` |
 | ACL denial (scope) | registry gate | `ChannelsOpen(CallFailed{ FORBIDDEN })` |
 | channel cap | wrapper `check_open` | `ChannelsOpen(CallFailed{ channel:too_many_channels })` |
-| **allocate failure** | pump handler, post-open | **`NegotiationRejected{ "allocate_failed" }`** |
 
 `TtySessionError::ChannelsOpen` now carries alkcall's typed
 `ChannelOpenError` verbatim (`#[from]`) instead of a flattened
@@ -170,7 +245,8 @@ on `establishment_reason()` without unwrapping strings.
   retry), `timeout` (maybe retry), `allocate_failed` (capacity —
   still distinguishable in-band).
 - The consumer's `open_via_channels` failure is a typed call error —
-  no peeking at the data stream for anything but `allocate_failed`.
+  no peeking at the data stream for anything but the (now
+  unreachable-from-registered-producers) error-frame formality.
 
 **Negative:**
 
@@ -180,9 +256,11 @@ on `establishment_reason()` without unwrapping strings.
   direct path's failure surface is unchanged.
 - The `channel:open_failed` reason codes the establisher emits join
   the wire-stable error set (ADR-049's one-way door).
-- `allocate_failed` remains a second, in-band failure shape on the
-  channels path — one residual asymmetry, pinned and documented until
-  `Establishment` gains a payload.
+- **Amendment (0.3.0):** allocation failure changed shape again —
+  `NegotiationRejected{ "allocate_failed" }` (in-band) →
+  `ChannelsOpen(CallFailed{ channel:open_failed, reason:
+  dial_failed })`. The direct path's `allocate_failed` frame is
+  unchanged (two transports, two contracts).
 
 ## Door type
 
@@ -205,12 +283,16 @@ ADR moves failure *reporting*, not the negotiation *location*.
 - ADR-009 (the open op's `input` is the negotiation; the R4
   amendment's in-band error frames — shrunk to `allocate_failed` by
   this ADR)
-- ADR-005 (kill-on-`Drop` — why establisher-side allocation is
-  unsound)
+- ADR-005 (kill-on-`Drop` — why a *second* establisher-side allocate
+  would be unsound; avoided by construction in the §2A amendment —
+  one allocate per open, consumed by the handler)
 - ADR-001 (the §5 `0x00` disambiguation — retained for the direct
-  path and the channels `allocate_failed` frame)
+  path; the channels-path peek is now a formality)
 - ADR-002 (backend selection/allocation ownership)
-- `src/channels.rs` — `make_tty_establisher`, `make_tty_open_handler`,
-  `tty_open_spec`
+- alkcall ADR-049 amendment 2 / review 007 R-01 (the `Establishment`
+  plan payload — the upstream capability this ADR's §2A adopts)
+- `src/channels.rs` — `make_tty_establisher`, `AllocatedHandle`,
+  `make_tty_open_handler`, `tty_open_spec`
 - `src/session.rs` — `TtySessionError::ChannelsOpen`, `open_via_channels`
-- `src/testing.rs` — the pinned `allocate_failed`-stays-in-band test
+- `src/testing.rs` — the pinned `allocate_failure_fails_open_as_dial_failed`
+  test (superseded `allocate_failure_still_arrives_in_band_on_channels_path`)