docs: implementation plan (TTY precedents folded in); task decomposition (17 tasks)

Plan updated with the alknet-tty findings: the drainer pattern
(single ordered writer) makes outbound chunk-boundary parsing sound;
TestStdinSink's try_send→Full→Pending is the inbound backpressure
precedent; OQ-01(a) now cites the reference.

Task graph (taskgraph-validated, 17 tasks, 6 generations, no cycles):
- tasks/server/: core-types, auth, healthz-decoy, adapter
- tasks/gateway/: dispatch, routes, publish
- tasks/websocket/: byte-adapter (research POC), upgrade-session, overlay-ops
- tasks/adapters/: from-openapi, from-jsonschema, to-openapi, from-wss, mcp
- tasks/client/: http-host
- tasks/infra/: integration-suite (phase 4)

Critical path runs through server core → adapter → WS session →
overlay tests → integration suite. High-risk tasks are the three WS
tasks, de-risked by the ws-byte-adapter POC blocking upgrade-session.

tasks/gateway/publish.md

@@ -0,0 +1,46 @@
+---
+id: gateway-publish
+name: POST /publish endpoint for Pub operations
+status: pending
+depends_on: [gateway-routes]
+scope: narrow
+risk: medium
+impact: component
+level: implementation
+tags: [gateway, phase-3]
+---
+
+## Description
+
+Implement `POST /publish` per ADR-068: NDJSON request body (each line =
+one published chunk) dispatched through `invoke_sink()` (alkcall
+ADR-046); handler's final ResponseEnvelope → 200 JSON or mapped error
+status. Resolve OQ-02 during this task: first line carries
+`{ "operation": "/{service}/{op}", "chunk": {...} }` (subsequent lines
+`chunk`-only); terminal errors are plain HTTP status + JSON body (not
+an NDJSON line). Client disconnect drops the body stream → sink
+cancelled (PublishStream sees EOF). Non-Pub target → 400
+INVALID_OPERATION_TYPE. Tests: multi-chunk publish round-trip against a
+SinkHandler over DuplexStream, early-disconnect, error mapping.
+
+## Acceptance Criteria
+
+- [ ] /publish wired; OQ-02 convention implemented and documented in ADR-068
+- [ ] Sink round-trip test (3+ chunks → final envelope)
+- [ ] Disconnect mid-stream cancels the handler (no hang)
+- [ ] to_openapi gateway doc gains /publish; gateway `info.version` minor bump
+- [ ] `cargo test` passes
+
+## References
+
+- docs/architecture/decisions/068-gateway-publish-endpoint.md
+- docs/architecture/open-questions.md (OQ-02)
+- alkcall ADR-046 (Pub/invoke_sink/PublishStream)
+
+## Notes
+
+> Agent fills during implementation.
+
+## Summary
+
+> Agent fills on completion.