chore: consume alkcall 0.6.0; OQ-TN-06 resolved by ADR-050

alkcall 0.6.0 landed the review 007 remediation (filed from this
crate's UDP POC pass):
- R-01: Establishment carries the plan (ADR-049 amendment 2) —
  typed-opaque ChannelPlan, OpenHandler gains the plan param, the
  wrapper threads it; the POC's side-channel HandleHandoff and its
  same-resource race are dead (the establisher returns the dialed
  handle: Ok(Establishment::new(plan)))
- R-02: OpenHandler JoinHandle lifetime contract documented (early
  return = teardown-at-birth) + yield-once acceptance flag and
  debug! birth-teardown hint
- R-03: pump_bidi pinned upstream (ADR-050) — two pumps,
  shutdown-on-completion, (u64, u64) copy counts, errors EOF-shaped

alktunnels updates:
- Cargo.toml: alkcall 0.5.0 -> 0.6.0 (lockfile resolves 0.6.0)
- AGENTS.md convention 8: use alkcall channels::pump_bidi, do not
  hand-roll; await it inline inside the OpenHandler's task
- AGENTS.md convention 11: pin note updated; amendment 2 marked
  load-bearing (Establishment::new replaces side-channel handoff)
- AGENTS.md convention 13: fixed ADR citation bug (was "alkcall
  ADR-024, ADR-050" — those are peer-graph-routing and pump-bidi;
  intended targets are alknet ADR-024/ADR-050 with their alkcall
  ports ADR-019/ADR-011)
- AGENTS.md architecture context: ADR-050 + ADR-049 amendment 2 rows
- phase-0-findings OQ-TN-06: RESOLVED — pump_bidi landed upstream;
  the POC is cited as convergence input alongside alktty and the
  assembly-layer copies; Phase 1 consumes the helper
- phase-0-findings OQ-TN-09: implementation note updated —
  Establishment::new(plan) replaces the handoff sketch
- poc-summary: resolutions addendum for both upstream findings
  (R-01/R-02/R-03 with the typed-opaque and (u64, u64) deviations
  recorded); references note 0.6.0 supersession

Verification: cargo test (0 tests, ok), clippy --all-targets
-D warnings, fmt --check, wasm32 check, doc --no-deps — all clean

docs/research/phase-0-findings.md

@@ -550,6 +550,19 @@ POC: the `OpenHandler` JoinHandle semantics (see `poc-summary.md` §
 Issues Surfaced #1) are where such a helper would pin the teardown
 contract.
 
+**RESOLVED 2026-09-07 — the helper landed upstream in alkcall 0.6.0**
+(review 007 R-03, ADR-050): `alkcall::channels::pump_bidi(channel,
+peer_read, peer_write) -> (u64, u64)`. Shape as this OQ sketched it —
+two pumps, shutdown-on-completion wired in, copy counts returned for
+observability, errors EOF-shaped (no `Err` state — a mid-stream error
+is an abrupt close, so an `io::Result` would be dead code). The POC
+is cited in the ADR as convergence input alongside alktty's channels
+session and the assembly-layer copies. alktunnels consumes it; the
+POC's `pump_halves` is now prior art only. The JoinHandle lifetime
+contract (R-02) is documented on the `OpenHandler` type: await the
+helper inline inside the handler's task — early return is
+teardown-at-birth.
+
 ### OQ-TN-07: ALPN strategy
 
 This crate owns the `alk/tunnel`-family ALPN(s). alkcall ADR-004: one
@@ -681,9 +694,14 @@ channel stream.
   the data stream.
 - Implementation note (ADR-049 amendment): the establisher takes
   `(input, auth)` only — the channel's yield-once `BiStream` belongs
-  exclusively to the pump handler. The tunnel establisher hands the
-  dialed connection to the pump handler through its own path (e.g. a
-  oneshot/`Arc<Mutex<Option<_>>>`), not via the open-op input.
+  exclusively to the pump handler. **Amendment 2 (alkcall 0.6.0,
+  review 007 R-01) filled the reserved `Establishment` field:**
+  `Establishment::new(plan)` carries the dialed handle to the pump
+  handler via its `plan` parameter (`ChannelPlan` — typed-opaque
+  `Arc<dyn Any + Send + Sync>`; downcast happens in this crate). The
+  POC's side-channel `HandleHandoff` is dead — no handoff map, no
+  same-resource race; the establisher just returns
+  `Ok(Establishment::new(dialed))`.
 - What remains for this crate's Phase 1 ADR (narrowed from the
   original frame-vocabulary question):
   - Half-open semantics: one direction EOFs, the other keeps pumping
@@ -827,7 +845,10 @@ Candidate reading for the research specialist (to be expanded):
       gives both shapes (producer `pump_halves`, consumer
       `take_halves` + copy): same shape modulo channel side; the
       alknet ADR-078 convergence test is satisfied, extraction now
-      decidable in Phase 1
+      decidable in Phase 1. **RESOLVED 2026-09-07:** the helper
+      landed upstream in alkcall 0.6.0 as `channels::pump_bidi`
+      (ADR-050, review 007 R-03) — this crate consumes it; see
+      OQ-TN-06
 - [x] OQ-TN-05 executable input (backend trait vs no-trait) — POC
       confirms stream substrates need no trait: `pump_halves` is
       generic over boxed halves (TCP `into_split`, UDP `UdpHalf`