refactor(gateway): migrate to alkcall 0.2 promoted gateway module

Bump the alkcall dependency to 0.2 (with the gateway feature) and
converge on the promoted shared pieces:

- The local dispatch spine (gateway/dispatch.rs, 721 lines) is deleted;
  GatewayDispatch, schema_disclosure_denial, and DEFAULT_DEADLINE are
  re-exported from alkcall::gateway (alkcall ADR-048). The 30 s default
  deadline preserves the previous behavior exactly.
- gateway/schema_cache.rs (PublishSchemaCache) is deleted: alkcall CF-003
  compiles publish_schema at registration time and exposes
  OperationRegistry::publish_validator; the /publish chunk stream
  resolves against it. Un-compilable schemas are now rejected at
  registration, so the two end-to-end fail-closed tests were reworked
  into a registration-rejection test (a stronger guarantee).
- schema_disclosure_denial consumers (to_mcp, routes) use alkcall's
  promoted implementation; the alkhttp-local copy is gone (ADR-071
  updated: the guard stays as defense-in-depth, the implementation no
  longer forks).
- CF-001: from_wss drop monitor and the WS overlay tests use
  CallError::connection_closed; the review-001-ws-eof-signal race tests
  now assert retryable CONNECTION_CLOSED on both resolution paths (the
  tolerated non-retryable INTERNAL write-failure outcome is gone).
- Added CHANGELOG.md (Keep a Changelog), Unreleased section records the
  bump and convergence.

Verification: cargo test default 453 ok, wss 470 ok, mcp 526 ok,
all-features 575 ok; clippy -D warnings clean (default + all-features,
all-targets); fmt clean; cargo doc warning-free.

Net: -1093 lines.

docs/architecture/README.md

@@ -68,7 +68,7 @@ types — the former `alknet-core` and `alknet-call` merged).
 | [068](decisions/068-gateway-publish-endpoint.md) | Gateway `/publish` Endpoint | 6th gateway endpoint for `OperationType::Pub` (producer→consumer streaming); NDJSON request body → `call.published` chunks |
 | [069](decisions/069-webtransport-out-of-scope.md) | WebTransport Out of Scope | h3/WebTransport removed from alkhttp scope entirely (an alknet concern); supersedes the deferral framing of ADR-044 |
 | [070](decisions/070-from-wss-consumer-adapter.md) | `from_wss` Consumer Adapter | Import a remote node's operations over WSS — same-protocol importer, channels-over-WS as transport; `wss` feature gate |
-| [071](decisions/071-dispatch-schema-guard.md) | Dispatch-Spine `services/schema` Op-Path Guard | `GatewayDispatch` applies the GET `/schema` visibility+ACL checks to the meta-op's inner `name` (review-002 PRJ-16); alkcall CF-004 is the complete fix, this stays as defense-in-depth |
+| [071](decisions/071-dispatch-schema-guard.md) | Dispatch-Spine `services/schema` Op-Path Guard | `GatewayDispatch` applies the GET `/schema` visibility+ACL checks to the meta-op's inner `name` (review-002 PRJ-16); alkcall CF-004 is the complete fix, this stays as defense-in-depth (now via the promoted `alkcall::gateway` shared check — spine + guard themselves live in alkcall per ADR-048) |
 
 ## Relevant Open Questions
 

docs/architecture/decisions/071-dispatch-schema-guard.md

@@ -53,23 +53,53 @@ registry rejects non-`Pub` operations before the handler runs and the
 sink ignores the input, so nothing is projected there.
 
 The visibility + ACL check itself is one shared function
-(`gateway::dispatch::schema_disclosure_denial`) used by the HTTP GET
-`/schema` route, the dispatch-spine guard, and the MCP `schema` tool,
-so the transports cannot drift.
+(`schema_disclosure_denial`) used by the HTTP GET `/schema` route, the
+dispatch-spine guard, and the MCP `schema` tool, so the transports
+cannot drift.
 
 ## Consequences
 
 - **Transport-level invariant (PRJ-16's wording):** no alkhttp
   transport can fetch, through any path, a spec the GET `/schema`
   route would deny for the same identity.
-- **When CF-004 lands, the guard stays.** The alkcall-side handler
-  check is the complete fix for every transport (wire, overlays, peer
-  composition); this per-transport check remains as defense-in-depth.
-  Do not remove it.
-- Wire-observable behavior changes only for the previously-leaking
-  requests: they now get the same 404/403 the GET route returns.
-  Legitimate `services/schema` calls (allowed inner names) are
-  unaffected.
+- **When CF-004 landed, the guard stayed — and was promoted.** The
+  alkcall-side handler check is the complete fix for every transport
+  (wire, overlays, peer composition; alkcall commit `8cb2a6e`). The
+  alkhttp spine, the GET `/schema` route, the MCP `schema` tool, and
+  the spine's `services/schema` op-path guard all now converge on the
+  **shared promoted implementation**: `alkcall::gateway::
+  schema_disclosure_denial` (alkcall ADR-048). The local copy was
+  deleted on the alkcall-0.2 bump — one implementation, so the
+  transports still cannot drift, and no alkhttp-local fork remains.
+  Do not re-introduce a local copy.
+- **The dispatch spine itself is promoted too.** `GatewayDispatch`
+  (the `invoke`/`invoke_streaming`/`invoke_sink` spine with the
+  root-`OperationContext` invariants and the inner-`name` guard) is
+  `alkcall::gateway::GatewayDispatch` (feature `gateway`, enabled
+  unconditionally by the alkcall dependency — the gateway endpoints
+  are this crate's sole invoke path, ADR-047). The alkhttp-local copy
+  was deleted; only the HTTP-specific layers remain here (the
+  CallError → HTTP mapping in `gateway::error`, NDJSON/SSE framing,
+  body caps, batch envelopes, and this ADR's original
+  FORBIDDEN-vs-spec-404 split on the GET route).
+- **`/publish` chunk validation is registry-backed.** The local
+  compile-once `PublishSchemaCache` was deleted: alkcall CF-003
+  compiles `publish_schema` at registration time and exposes the
+  cached validator as `OperationRegistry::publish_validator`. The
+  `/publish` chunk stream resolves against that cache; the
+  fail-closed guarantee moved upstream with it (an un-compilable
+  schema is a registration error, so an unvalidated-ingest path
+  cannot be constructed).
+- **CF-001 resolution:** alkcall's `CallError::connection_closed`
+  (retryable `CONNECTION_CLOSED`) covers the write-failure race; the
+  from_wss drop-monitor race tests assert retryable-only (the
+  previously-tolerated non-retryable `INTERNAL: failed to write
+  request frame` outcome is gone from the wire vocabulary on the
+  undelivered-request path).
+- Wire-observable behavior is unchanged from the pre-promotion guard:
+  previously-leaking requests still get the same 404/403 the GET
+  route returns; legitimate `services/schema` calls (allowed inner
+  names) are unaffected.
 - The guard matches the outer registration's `spec.name` against the
   `services/schema` constant rather than the raw request string, so
   leading-slash variants (`/services/schema`) hit the same check.