Module refresh 

Background refresh scheduler for dynamic pipeline sources.

Manages per-source refresh loops based on RefreshPolicy:

• Interval(duration): re-fetches on a timer
• Watch: uses file system notifications (via notify)
• Push: receives updates from external triggers (NATS)
• OnDemand: only refreshes when explicitly triggered via API/signal

Structs

RefreshResult

Notification sent when sources have been refreshed.

RefreshScheduler

Manages background refresh tasks for dynamic sources.

Enums

RefreshTrigger

A message requesting source re-resolution.

Constants

NATS_CONTROL_SUBJECT

The default NATS control subject for triggering source re-resolution.