v0.4.0 — Async Duck cancellation, retry & execution context

Added

• Abort-based cancellation for Async Ducks
• Execution-scoped AbortSignal propagation via executionAsyncContext
• First-class retry support with delay and backoff
• Explicit refresh() execution intent

Changed

• Unified async execution lifecycle for all ducks
• Cancellation no longer surfaces as an error
• Retry logic is fully observable (isRetrying)

Fixed

• Race conditions between cancel / retry / refresh
• In-flight execution leaks on unmount
• Inconsistent loading state during aborted runs

Notes

• Cancellation is propagated automatically through executionAsyncContext
• Transport layer needs to wire the signal once (axios / fetch)