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/dispatch.md

@@ -0,0 +1,47 @@
+---
+id: gateway-dispatch
+name: GatewayDispatch — shared dispatch spine (invoke + streaming)
+status: pending
+depends_on: [server-core-types]
+scope: moderate
+risk: medium
+impact: component
+level: implementation
+tags: [gateway, phase-1]
+---
+
+## Description
+
+Port the dispatch spine from
+`/workspace/@alkdev/alknet/crates/alknet-http/src/gateway/dispatch.rs`
+to alkcall's API: `GatewayDispatch::new(registry, identity_provider)`,
+`invoke()` (identity resolve → root OperationContext →
+`OperationRegistry` invoke → ResponseEnvelope), and `invoke_streaming()`
+(`BoxStream<ResponseEnvelope>` for Sub ops). The security invariants
+must hold identically across both: `External`-only (Internal →
+NOT_FOUND), `AccessControl::check` gating, no env-var reads. Port the
+error mapping (`gateway/error.rs`) too: CallError → HTTP status per
+docs/architecture/http-server.md §Error Mapping (NOT_FOUND→404,
+FORBIDDEN→401/403, INVALID_INPUT→422, TIMEOUT→504, INTERNAL→500,
+`HTTP_<status>` passthrough, retryable→Retry-After hint).
+
+## Acceptance Criteria
+
+- [ ] `invoke()` + `invoke_streaming()` ported against alkcall dispatch
+- [ ] Error mapping table ported with unit tests per row
+- [ ] Internal ops → 404 before ACL; ACL failure → 401/403 distinction preserved
+- [ ] `cargo test` passes
+
+## References
+
+- docs/architecture/http-server.md (§HTTP-to-call dispatch, §Error Mapping)
+- docs/architecture/decisions/023-operation-error-schemas.md
+- alkcall ADR-016 (error schemas), ADR-017 (privilege model)
+
+## Notes
+
+> Agent fills during implementation.
+
+## Summary
+
+> Agent fills on completion.