The part of a client that a config reload replaces: the routing
rules and the providers they name. Swapped as one unit, so a signal
never sees new routes with old providers.
The assembled pipeline: validate -> record -> route -> deliver ->
complete. The signal is saved before delivery starts, so it survives
a process exit mid-delivery as pending, and each provider’s
outcome is saved as soon as it is known. A sink failure is logged
and never stops delivery.