test(linear): add orchestration integration test against real createTaskCore (unit mocks hid 3 dev bugs)

[isadeks]

Component

API or orchestration, Tests / CI

Describe the gap

The #247 Mode A orchestration unit tests all mock createTaskCore, so none exercise the real task-creation persistence + validation path. The first dev smoke surfaced three bugs that every unit test missed precisely because of this:

1. Idempotency key rejected — releaseChild built ${orchestration_id}#${sub_issue_id}, but createTaskCore validates against /^[a-zA-Z0-9_-]{1,128}$/; the # 400'd and children silently never started. Mocked createTaskCore never ran the validator.
2. Reconciler read orchestration_id top-level — but createTaskCore persists channel metadata as a nested channel_metadata MAP. The mocked tests used an unrealistic top-level stream image and passed.
3. Reconciler OOM at 256MB — only observable at runtime.

Proposed solution

Add an integration test that runs the orchestration release/reconcile path against the real createTaskCore and a real DynamoDB (DynamoDB Local or aws-sdk-client-mock with realistic persisted shapes), asserting:

• a released child produces a TaskRecord whose channel_metadata.orchestration_id round-trips,
• the idempotency key is accepted by the real validator,
• the reconciler's stream parser reads the id from the persisted record shape (not a hand-built top-level image).

Acceptance criteria

• An integration test exercises releaseChild → real createTaskCore → real persisted record → reconciler stream parse, end to end.
• The test would fail against any of the three bugs above (regression coverage).
• Runs in CI without AWS credentials (DynamoDB Local or equivalent).

Related

• feat(linear): parent/sub-issue orchestration with dependency-aware child tasks #247 (Mode A orchestration)
• Bugs fixed in feat/247-reconciler (idempotency key, nested-metadata read, reconciler memory).