feat(review 008 Unit 3c): the gate-2 e2e harness; 0.8.0 release bookkeeping

- src/channels/gate2_tests.rs (ADR-051 gates 6/7, review 008 gate 2):
  the full consumer -> hub (HubLegTemplate) -> spoke relay e2e —
  the open resolves with the hub-allocated channel_id, `bound`
  survives the relay, data flows both directions with a fake 8-byte
  chunk header riding verbatim (the hub never parses the data plane,
  ADR-034/035), spoke-side close cascades to clean reclaim on both
  legs; hub-side disconnect (the consumer's duplex end dropped via a
  killable transport proxy) tears down both legs with the ledger
  decremented; the mid-establishment window (ADR-051 §6) pinned with
  its two reclaim signals — the consumer leg reclaims at its own
  transport EOF, the spoke channel (allocated before the establisher
  replied) is the honest residual, reclaimed when the spoke-leg
  transport ends; the channels/tty/sub standard-shape companion pins
  no derivation regression.
- src/channels/relay.rs: the relay's adopted producer-leg channel
  entry now reclaims when the relayed pump completes (teardown after
  pump_bidi) — the consumer-leg wrapper's teardown cannot see the
  producer leg's manager; the RelayPlan carries the spoke id for the
  reclaim.
- Release bookkeeping: 0.7.1 -> 0.8.0, the CHANGELOG entry covering
  Units 1-3 (Establishment reply projection, open_channel_with_reply,
  flavor-form discovery derivation, ChannelRelay, HubLegTemplate,
  gate-2 harness); review 008 Status -> Resolved with the U-1/U-2
  commit refs and the 955->945 errata note; ADR-051 Status ->
  all units landed + the §6 mid-establishment residual expanded to
  the two-reclaim-signal shape the gate pins; the stale "0.7.2"
  version mentions in ADR-047/049 corrected to 0.8.0 (the units land
  unreleased).

Verification: cargo test 669 passed / 0 failed; clippy --all-targets
-- -D warnings clean; fmt --check clean; cargo doc --no-deps clean;
cargo check + clippy on wasm32-unknown-unknown clean;
cargo publish --dry-run --allow-dirty passed.

docs/architecture/decisions/047-openable-alpns-are-operations.md

@@ -86,7 +86,7 @@ pinned by test). The `op_name_is_standard_channel_open_shape` helper
 and the strip-last derivation are two-way-door implementation details
 within the one-way wire shape.
 
-Implemented surface (alkcall 0.7.2): the generalized
+Implemented surface (alkcall 0.8.0): the generalized
 `derive_alpn_from_op_name` (strip-last), the explicit-field emission
 (`spec_to_json_pub` + the advertised schema property), and the
 preference order in `rebuild_spec_for`. Verification gates landed as