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

Cargo.lock

@@ -27,9 +27,9 @@ dependencies = [
 
 [[package]]
 name = "alkcall"
-version = "0.5.0"
+version = "0.6.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "0bbaeb718c370b74f9136d1d59b4608249bd7d1dd2332c0259f98351d709737f"
+checksum = "a44500900b82904d2a870e444051fc041a042e42ff7190803bbc5b3973f4feeb"
 dependencies = [
  "async-trait",
  "bytes",