When the alert manager suppresses an alert because it is flapping, today
the suppression is silent: the operator sees no alert and no diagnosis.
That trains people not to trust Pulse on flapping resources -- the
detector did its job, but the user just sees absence.
Add a one-shot Manager callback that fires exactly when a tracking key
crosses from quiet into the flapping cooldown window. The callback is
the hook downstream surfaces (patrol, findings) will use to explain
what is flapping and why Pulse stopped notifying.
Lock-safety: checkFlappingLocked now returns (suppress, justTransitioned).
The caller (dispatchAlert) reads the transition signal, then dispatches
the callback from a fresh goroutine. The alerts manager mutex is never
held while the callback runs, so subscribers may take their own locks
or re-enter the alerts package without deadlock.
Subsequent dispatches inside the cooldown window remain silent: the
transition flag is only set on the call that flips flappingActive from
false to true.
rcourtman
fa9cc5d691