0.87.13 followup. The Cancelled publish had no asserting test —
mechanical revert of the publish block shipped green. New sqlx test
subscribes before spawn, drives SlowDispatcher into flight, cancels,
asserts both Started and Cancelled frames with breadcrumb fields.
Mutation-confirmed.
Also corrects: cron-test rationale comment (inverted unlock-axis),
Cancelled docstring (self-contradicting clear-triggers sentence).
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>