feat(review 006 Unit 2): additive OperationSpec.description disclosed via discovery (E-02)

- OperationSpec gains description: Option<String> (builder
  with_description, defaults None; no struct-literal construction
  sites exist, so additive by construction)
- spec_to_json_pub emits description when set; rebuild_spec_for
  parses it back — the field survives from_call discovery and
  op/register announcement (same round-trip pattern as
  resource_id_path / publish_schema)
- services/list and the local-ops half of services/list-peers emit
  description when set; output-schema docs on both listing specs and
  operation_spec_schema advertise the field
- Tests: builder/default, emit/omit, listing emission, schema
  disclosure, schema-doc presence, round-trip + absent-stays-absent
  (8 new; 616 total)
- Docs: review 006 Unit 2 marked IMPLEMENTED; ADR-047 §6 amendment
  records the E-02 discovery decision (listing enrichment lands, the
  channel/resources/subscribe half stays deferred); OQ-40 gains the
  load-bearing note; operation-registry.md struct + listing docs;
  CHANGELOG

Verification: cargo test (616 pass), clippy -D warnings (host +
wasm32), fmt --check, cargo doc --no-deps, wasm32 check — all clean

docs/reviews/006-channel-open-establishment-gap-review.md

@@ -27,7 +27,13 @@ gates landed as tests; two implementation-shape notes recorded in
 ADR-049's amendment: the establisher does not receive the channel
 `Connection` (yield-once BiStream belongs to the pump handler), and
 the bound is the earlier of dispatch deadline and per-registration
-timeout). The original remediation sketch below is superseded by the
+timeout). **Unit 2 (E-02) is implemented** in alkcall 0.5.0
+(`OperationSpec.description: Option<String>` +
+`with_description`, `spec_to_json_pub` emits it when set,
+`rebuild_spec_for` parses it (shared by `from_call` and `op/register`),
+`services/list` and `services/list-peers` local listings emit it when
+set; the ADR-047 §6 amendment below records the discovery decision).
+The original remediation sketch below is superseded by the
 "Remediation plan (post-verification)" section; the original sketch
 is retained for the record.
 
@@ -360,6 +366,10 @@ transports, two contracts). alkhttp unaffected (no openable ops).
 small ADR amendment: recommend (3) — subscribe for live resource sets
 (the decided shape, now load-bearing), plus an additive
 `description` field on the listing (cheap, immediately useful).
+**Implemented 2026-09-06 (alkcall 0.5.0):** the listing half landed
+(`OperationSpec.description`, four touchpoints as the appendix
+corrected); the subscribe half stays deferred (OQ-40, now with the
+load-bearing note).
 
 **Unit 3 — E-03/E-04.** E-03: log-or-comment; E-04: doc note. Trivial.
 
@@ -407,7 +417,9 @@ correction): struct field + `spec_to_json_pub` emit +
 `services/list` emits it when set. OQ-40 stays deferred but gains a
 "load-bearing for alktunnels discovery UI" note; the
 `channel/resources/subscribe` half stays deferred (alktunnels v1 uses
-config-known op names).
+config-known op names). **Status: IMPLEMENTED (2026-09-06)** — the
+discovery decision (3: enriched listing now, subscribe deferred) is
+recorded as an amendment to ADR-047 §6.
 
 **Unit 3 — E-03/E-04/N-2 (trivial batch, same PR series as Unit 1).**
 E-03: debug log (or pinning comment) on the discarded `UnknownChannel`