fix(core): MessageBus.request() silently hangs 60s when publish() fails

[TravisHaa]

Bug Description

MessageBus.request() contains a floating promise that causes two failure modes when publish()
rejects:

1. The rejection is routed to this.emit('error', error) on the EventEmitter. If no error
   listener is registered at call time, Node.js throws an uncaught exception and crashes the
   process.
2. Even with an error listener, the Promise returned by request() silently hangs for the full
   60-second timeout instead of failing fast — the caller gets no immediate signal that the publish
   failed.

Root Cause

In packages/core/src/confirmation-bus/message-bus.ts, inside the new Promise() constructor
callback, this.publish() is not awaited and has no .catch() chain:

// eslint-disable-next-line @typescript-eslint/no-floating-promises,
@typescript-eslint/no-unsafe-type-assertion
this.publish({ ...request, correlationId } as TRequest);

Fix

Chain .catch(reject) on the publish call so any publish failure immediately cancels the timeout and rejects the caller. This affects any code path that calls messageBus.request() — including the planned STEP_THROUGH_REQUEST/RESPONSE flow in step-through mode, where a malformed message would deadlock the scheduler for 60 seconds.

[cocosheng-g]

Triage Summary

This bug report identifies a critical error handling flaw in the MessageBus core utility, which can lead to process crashes or silent hangs. Because fixing this requires modifying core internal data structures and IPC mechanisms, it requires deep architectural alignment and maintainer oversight. Therefore, I have categorized this as Maintainer-only.