Extracts state machine graph structure from a compiled TLX.Spec module.

Shared by all diagram emitters (DOT, Mermaid, PlantUML, D2). Returns a struct with states, edges, initial state, and module name.

Usage

graph = TLX.Emitter.Graph.extract(MySpec)
graph = TLX.Emitter.Graph.extract(MySpec, state_var: :status)

graph.states   #=> MapSet<[:idle, :running, :done]>
graph.edges    #=> [{:idle, :running, "start"}, ...]
graph.initial  #=> :idle
graph.name     #=> "MySpec"