docs(tasks): decompose review 001 remediation Units 1-5 into taskgraph tasks

21 review-001 tasks across server/adapters/client/gateway/websocket/infra,
chunked from the 7-unit remediation plan in
docs/reviews/001-initial-implementation-review.md.

- Scope split by mechanism, not one-per-finding: 15 tasks in generation 1
  (parallelizable), 6 sequenced after their file-sharing precursors
- Deliberately deferred until dependent fixes land: projection/doc
  fidelity partial (Unit 6 beyond dependency hygiene), coverage backfills
  (COV-01..07 via in-task acceptance for forward.rs), and per-finding
  minors (OAI-06/07, HY-02/04/06/10/11, CON-08)
- Cross-crate WS-12 (alkcall demux 4 GiB discard alloc) noted for filing
  in alkcall, not here

taskgraph: validate clean, no cycles, 6 generations

tasks/gateway/review-001-gateway-stream-errors.md

@@ -0,0 +1,75 @@
+---
+id: review-001-gateway-stream-errors
+name: Gateway error-fidelity — SSE terminality, mappings, Retry-After, deadline (GW-03..GW-07, GW-12..GW-14)
+status: pending
+depends_on: []
+scope: narrow
+risk: low
+impact: component
+level: implementation
+tags: [gateway, review-001]
+---
+
+## Description
+
+Review 001 gateway error-fidelity findings
+(`src/gateway/routes.rs`, `error.rs`, `dispatch.rs`) — the response a
+caller sees must match the documented contract and match across
+transports:
+
+- **GW-04**: SSE error events are not terminal — the stream continues
+  after `Err` (`routes.rs:299-313`) while the wire dispatcher treats
+  `Err` as terminal; two transports disagree about stream semantics
+  (http-server.md:219-223 documents terminal). Emit the error frame and
+  end the stream (`take_while`).
+- **GW-03**: `INVALID_OPERATION_TYPE` → 500 on `/call`//`/batch` (client
+  fault reported as server fault; pollutes alerting) but 400 on
+  `/publish`. Map consistently (400 or 422) and document in
+  http-server.md.
+- **GW-05**: the 30 s `DEFAULT_TIMEOUT` deadline is recorded
+  (`dispatch.rs:34,165`) but never enforced — a hung handler holds the
+  request open indefinitely. Either enforce (`tokio::time::timeout`
+  around Once-op invokes) or remove the dead metadata. Prefer enforcing;
+  it is the documented contract.
+- **GW-07**: `Retry-After` machinery exists in
+  `call_error_to_http_response` (`error.rs:61-75`) but the main gateway
+  error path builds responses by hand (`routes.rs:319-333`) — retryable
+  `HTTP_429`/`HTTP_503` reach callers with no `Retry-After` despite the
+  documented mapping. Route gateway error responses through the shared
+  mapper.
+- **GW-12**: ACL denial on `/subscribe` surfaces as HTTP 200 +
+  `event:error` while `/call` returns 401/403. ADR-049 makes
+  200-on-stream defensible, but the doc must call out the asymmetry —
+  coordinate with review-001-output-projection (PRJ-05) which documents
+  it.
+- **GW-13**: no SSE keep-alive/heartbeat (`routes.rs:172`) — quiet-but-
+  alive streams (the normal state for subscriptions) die at LB/proxy
+  idle timeouts. Add keep-alive + `retry:` field.
+- **GW-14**: stale module doc (`routes.rs:1-9` claims `/publish` is "a
+  separate module"; AGENTS.md §7's "5 gateway endpoints" framing is
+  similarly stale — ADR-068 made it 6).
+
+## Acceptance Criteria
+
+- [ ] SSE stream ends after an error event (test); keep-alive present
+- [ ] `INVALID_OPERATION_TYPE` maps to the same status on `/call`, `/batch`, `/publish`; http-server.md table updated
+- [ ] Once-op invokes enforce the 30 s deadline (test with a hung handler)
+- [ ] Retryable errors carry `Retry-After` on all live error paths (test)
+- [ ] GW-14 docs fixed (module doc; AGENTS.md gateway-endpoint count if touched)
+- [ ] `cargo test` and `cargo clippy --all-targets -- -D warnings` pass
+
+## References
+
+- docs/reviews/001-initial-implementation-review.md (Part C, GW-03..GW-07, GW-12..GW-14)
+- docs/architecture/decisions/049-streaming-handler-for-subscriptions.md
+- docs/architecture/decisions/023-operation-error-schemas.md
+
+## Notes
+
+> Agent fills during implementation. Independent of
+> review-001-gateway-publish-semantics (both touch routes.rs —
+> sequence or coordinate to avoid churn).
+
+## Summary
+
+> Filled on completion.