Abortable Helpers (Timeout + Composed Abort)

Challenge summary

Coordinate timeouts and abort signals so asynchronous work stops promptly and cleans up its listeners and timers.

What you'll practice

• Reject timed-out work with a clear reason and clear its timer.
• Handle signals that are already aborted before work begins.
• Compose multiple signals while preserving the first abort reason.

What Premium unlocks

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