World boot probes settle and cancel

Status: Accepted. Date: 2026-09-29. Card t_9360174c, task t_7279cb9a.

The Dub browser diagnostic retained a World boot with no completed services after its twin host began answering. down refused because boot owned the instance; the foreground up cancellation handler accepted SIGINT but did not return. The pinned runtime's boot-identity request awaited only response end or request error. A response that aborts after headers need not emit an error on the request, and this promise did not observe the boot AbortSignal.

The identity probe now has a one-second deadline independent of socket inactivity. Response error, abort or premature close and request error/close settle the probe. Cancellation destroys the request and settles the promise, then the enclosing boot checks its AbortSignal and rolls back through its existing owner. Completion clears the deadline and abort listener. An absent identity answer keeps the existing legacy-twin semantics; an observed mismatched boot identifier still refuses the service.

This fixes a general lifecycle wait, without changing an application's code, forging a vendor response, or directly stopping World-owned infrastructure. The original diagnostic does not by itself prove which missing terminal event occurred; the retained source defect covers those endings and cancellation explicitly. No automated tests were run, as the owning card prohibits them. Build and real World/browser observations are recorded on the card; the whole card receives its independent review after coding.