chore(deps): consume alkcall 0.7.0 — CONNECTION_CLOSED maps 503

Dependency wave + one wire-surface behavior fix:

- bump alkcall 0.6 -> 0.7 (gateway feature unchanged). No code change
  forced: this crate constructs no ServingConfig (the one 0.7.0
  struct-literal break — from_wss keeps the pure-consumer
  from_connection; opt-in serving remains the review-006 Part C
  deferred decision), and the CF-006 per-call opener-identity overlay
  is behavior-only upstream (hub-forwarded WS-ferry opens now resolve
  the end client's identity, the intended effect)
- gateway error table maps CONNECTION_CLOSED -> 503 Service
  Unavailable: alkcall 0.7.0's CF-007 amendment makes it the eighth
  protocol code (ADR-016's list is formal at eight); it previously
  fell to the catch-all 500, misreporting a retryable,
  provably-undelivered call as a permanent server failure. retryable:
  true, so the retry_after details path applies on 503. Tests pin the
  mapping and the Retry-After passthrough
- ADR-023 amended: the protocol-code list is eight (ALREADY_EXISTS +
  CONNECTION_CLOSED rows added to the §3 table, normative rule and
  call.error code list updated); http-adapters.md six-code references
  de-staled

Verification: cargo test (456 passed), cargo test --all-features
(589 passed), clippy -D warnings (default + all-features), fmt
--check, cargo doc --no-deps (0 warnings)

docs/architecture/decisions/023-operation-error-schemas.md

@@ -4,21 +4,25 @@
 
 ## Status
 
-Accepted (amended by alknet ADR-049 — protocol-level code list extended to six; alkcall ADR-021)
+Accepted (amended by alknet ADR-049 — protocol-level code list extended to six; alkcall ADR-021; alkcall 0.7.0 CF-007 — the list is eight: `ALREADY_EXISTS` (alkcall ADR-022, mapped 409 Conflict by review 006 UP-01) and `CONNECTION_CLOSED` (alkcall ADR-016 CF-001, mapped 503 Service Unavailable in this crate's gateway error table))
 
 ## Context
 
 The `OperationSpec` in the call crate (now alkcall) has `input_schema` and
 `output_schema` but no `error_schemas`. The `call.error` payload (the alkcall
 crate's `call-protocol.md`) carries a `code` and `message`, where `code` is
-one of six infrastructure codes: `NOT_FOUND`, `FORBIDDEN`, `INVALID_INPUT`,
-`INVALID_OPERATION_TYPE`, `INTERNAL`, `TIMEOUT`.
+one of eight infrastructure codes: `NOT_FOUND`, `FORBIDDEN`, `INVALID_INPUT`,
+`INVALID_OPERATION_TYPE`, `INTERNAL`, `TIMEOUT`, `ALREADY_EXISTS`,
+`CONNECTION_CLOSED`.
 
-These six codes cover **protocol-level failures** — the call protocol
+These eight codes cover **protocol-level failures** — the call protocol
 itself can always fail to find an operation, deny access, reject bad input,
-reject the wrong dispatch method for the operation type, time out, or hit
-an internal error. They are emitted by the dispatch machinery (the registry,
-the adapter), not by operation handlers. `INVALID_OPERATION_TYPE` was added
+reject the wrong dispatch method for the operation type, time out, hit an
+internal error, reject an `op/register` collision (`ALREADY_EXISTS`, alkcall
+ADR-022), or observe a provably-undelivered call (`CONNECTION_CLOSED`,
+alkcall ADR-016 CF-001 — the only retryable protocol code). They are emitted
+by the dispatch machinery (the registry, the adapter), not by operation
+handlers. `INVALID_OPERATION_TYPE` was added
 by alknet ADR-049 (streaming handler for subscriptions — now alkcall ADR-021;
 `invoke()` called on a `Sub`, or `invoke_streaming()` on a `Query`/`Mutation`).
 
@@ -173,8 +177,8 @@ optional-array convention.
 
 - `code` — the error code. Either a protocol-level code (`NOT_FOUND`,
   `FORBIDDEN`, `INVALID_INPUT`, `INVALID_OPERATION_TYPE`, `INTERNAL`,
-  `TIMEOUT`) or an operation-level domain code from `error_schemas` (e.g.,
-  `FILE_NOT_FOUND`, `RATE_LIMITED`).
+  `TIMEOUT`, `ALREADY_EXISTS`, `CONNECTION_CLOSED`) or an operation-level
+  domain code from `error_schemas` (e.g., `FILE_NOT_FOUND`, `RATE_LIMITED`).
 - `message` — human-readable error message. Unstructured — for logging and
   debugging, not for programmatic handling. Consumers should switch on
   `code`, not parse `message`.
@@ -190,8 +194,8 @@ optional-array convention.
 
 ### 3. Protocol-level vs operation-level error codes
 
-The six existing codes are **protocol-level** — emitted by the dispatch
-machinery, not by handlers:
+The eight protocol-level codes are **protocol-level** — emitted by the
+dispatch machinery, not by handlers:
 
 | Code | Emitted by | Meaning |
 |------|-----------|---------|
@@ -201,6 +205,8 @@ machinery, not by handlers:
 | `INVALID_OPERATION_TYPE` | Registry / `OperationEnv` | Wrong dispatch path for the operation's type (`invoke()` on a `Sub`, `invoke_streaming()` on a `Query`/`Mutation`, `invoke_sink()` on a `Query`/`Mutation`/`Sub`, or `OperationEnv::invoke()` on a `Sub` during composition — alkcall ADR-021; `Pub` ops dispatch via `invoke_sink()`, alkcall ADR-046) |
 | `INTERNAL` | Registry / Adapter | Handler panic, unhandled error, connection failure |
 | `TIMEOUT` | Adapter | Request timed out |
+| `ALREADY_EXISTS` | Registry / collision gate | `op/register` collision — a peer-announced op may not replace the serving side's own registrations (alkcall ADR-022 G-03) |
+| `CONNECTION_CLOSED` | Client write path | The `call.requested` frame could not be written — the call is provably undelivered (alkcall ADR-016 CF-001). `retryable: true` — the only protocol code a caller may auto-retry. |
 
 Operation-level domain codes are emitted by **handlers** — the operation's
 own logic determines what went wrong. They are declared in `error_schemas`
@@ -251,9 +257,9 @@ accordingly.
 ```
 
 **Normative rule (review #002 W20)**: `from_openapi` must not produce error
-codes that collide with the six protocol-level codes (`NOT_FOUND`,
+codes that collide with the protocol-level codes (`NOT_FOUND`,
 `FORBIDDEN`, `INVALID_INPUT`, `INVALID_OPERATION_TYPE`, `INTERNAL`,
-`TIMEOUT`). The adapter prefixes
+`TIMEOUT`, `ALREADY_EXISTS`, `CONNECTION_CLOSED`). The adapter prefixes
 imported error codes with `HTTP_` and the status number (e.g., `HTTP_404`,
 `HTTP_429`) to avoid collision. This is a requirement for the adapter, not
 a naming convention — the `from_openapi` example above was previously shown

docs/architecture/http-adapters.md

@@ -553,8 +553,9 @@ for the factoring recommendation (thin shared struct, not a trait).
 `from_openapi` maps OpenAPI non-2xx response status codes to
 `ErrorDefinition`s (alkcall ADR-016 §5). The normative rule (review
 #002 W20): `from_openapi` must not produce error codes that collide
-with the six protocol-level codes (`NOT_FOUND`, `FORBIDDEN`,
-`INVALID_INPUT`, `INVALID_OPERATION_TYPE`, `INTERNAL`, `TIMEOUT`). The
+with the protocol-level codes (`NOT_FOUND`, `FORBIDDEN`,
+`INVALID_INPUT`, `INVALID_OPERATION_TYPE`, `INTERNAL`, `TIMEOUT`,
+`ALREADY_EXISTS`, `CONNECTION_CLOSED`). The
 adapter prefixes imported error codes with `HTTP_` and the status
 number:
 
@@ -601,7 +602,7 @@ request-level cap failure (422; GW-16 unified it with the
 `INVALID_INPUT → 422` mapping — it was hand-rolled as 400 before
 review-002). `BatchResultEntry.error` references
 the `BatchError` component (review-002 PRJ-16b): the serialized
-`CallError` as a oneOf over the six protocol-code envelopes plus a
+`CallError` as a oneOf over the protocol-code envelopes plus a
 generic arm carrying the operation-declared codes. See alkcall ADR-016.
 
 ## Why