Module topology 

Core-level topology-change notification primitive.

The topology sink receives events when nodes are registered, torn down, or have their deps mutated. This is the substrate for reactive describe() and reactive observe() at the graph layer.

Topology sinks are NOT nodes — they sit outside the reactive graph to avoid circularity (registering an observer node would itself be a topology change).

Enums

TopologyEvent

What changed in the topology.

Type Aliases

TopologySink

Callback for topology changes. D246/S2c/D248: single-owner ⇒ no Send + Sync (fires owner-side; the bound was shared-Core-era legacy).

TopologySubscriptionId

Identifier for a topology subscription (S2b / D225). Returned by super::node::Core::subscribe_topology; pass it to super::node::Core::unsubscribe_topology to deregister. The core-level RAII TopologySubscription is retired for the same reason as crate::node::SubscriptionId (D223: owned relocatable Core, no parameterless-Drop reach). Binding-layer RAII wraps unsubscribe_topology where the holder co-owns the Core.