chore: consume alkcall 0.7.0; W1/CF-005 resolved — identity seam validated

alkcall 0.7.0 resolved every open downstream-consumer finding,
including this crate's reverse-flow POC W1 (filed as ledger CF-005,
with the CF-006 corollary):
- CF-005 (a): ServingConfig.identity — the explicit override
- CF-005 (b): transport Connection::identity() propagates to
  channel 0 — set_identity before dialing is the mTLS/QUIC path
- CF-006: the establisher/pump handler receive the per-call opener
  identity (dispatch-resolved), not the install-time context
- CF-007: ADR-016 code list completed (doc-only)
- F-1 (POC finding): the ChannelPlan type doc now carries the
  Send + Sync payload constraint

alktunnels updates:
- Cargo.toml: alkcall 0.6.0 -> 0.7.0 (lockfile resolves 0.7.0)
- AGENTS.md convention 11: pin note updated; the 0.7.0 identity
  surface marked load-bearing (precedence order + per-call opener)
- AGENTS.md architecture context: CF-005/CF-006 row added; the
  'What the POC does NOT settle' list replaced with the accurate
  settled state (Phase 0 complete; Phase 1 = the spec)
- reverse-poc-summary: W1 marked RESOLVED with the remediation
  validated from the POC's topology (16 tests over 0.7.0: transport
  identity alone authorizes, ServingConfig.identity overrides,
  identity-less fails closed, CF-006 witness); F-1 marked documented
  upstream; what-the-POC-does-not-validate and verification blocks
  updated
- phase-0-findings OQ-TN-10: reverse POC entry notes the 0.7.0
  re-validation and W1 resolution

The reverse POC (/workspace/alktunnels-reverse-poc, 8b35818) re-
validated: the default harness now authorizes on transport identity
alone — the 0.6.0-era auth_token workaround is dead code.

Verification: cargo test, 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 = "0.6.0"
+version = "0.7.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "a44500900b82904d2a870e444051fc041a042e42ff7190803bbc5b3973f4feeb"
+checksum = "5162a10144df65b03b887e30f77eb30d956ca1ca460a3f81b409128cbcae3199"
 dependencies = [
  "async-trait",
  "bytes",