notify.sx: reminders + digests as durable flows over an injected transport.
A flow requests delivery (suspend); the host dispatch sends and resumes with
the outcome. At-least-once + idempotent (transport dedups by msg id; replay
logs outcomes). Retry rides suspend/resume with distinct per-attempt tags,
bounded by maxn. Digest delivers a batch with per-message outcomes.
182/182 green. Delivery core is the delivery-on-sx extraction seam.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
