Constant ACTION_SERVER_PUBLISHERS 

pub const ACTION_SERVER_PUBLISHERS: usize = 2;

Publishers an action SERVER creates, per action, beyond anything the author declares: the feedback topic and the status topic (create_publisher calls below). A consumer sizing the backend’s publisher table from a declaration must add these, because an ENTITIES action_server:... spec declares ONE entity and costs two publisher slots.

Same rule as ACTION_SERVER_QUERYABLES, and defined for the same reason: the number lives next to the calls that decide it, so it cannot drift from them without failing the gate that ties the two together.