agent2: Emit cancellation stop reason on cancel (#36381)

Release Notes:

- N/A

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Co-authored-by: Antonio Scandurra <me@as-cii.com>
ea828c0c59Ben Brandt committed on 8/18/2025, 7:58:30 AM· committed by GitHubparentb3969ed
2 files changedLine totals unavailable