Deliver Claude agent updates through root PostToolBatch and Stop hook context
without interrupting running tools. Defer to the durable next-turn queue after
five seconds without a boundary, or when the update contains attachments.

Let human steering and immediate controls pass a waiting boundary delivery.
Revoke pending updates on Stop and task disposal, and refresh completion
pointers when only part of a task cohort remains unacknowledged.

Keep native human steering and other providers' delivery behavior unchanged.
Exercise the real send service, hook adapter, outbox ordering and ownership
races with deterministic regression coverage.

Upstream-PR: https://github.com/pingdotgg/t3code/pull/21158
Co-Authored-By: GPT-6.1 Sol at high effort, implementation and SDK research <noreply@openai.com>
Co-Authored-By: GPT-6.1 Sol at xhigh effort, independent review <noreply@openai.com>