Module core 

Core runtime primitives: Engine + Ctx + State + Config.

Modules

config

EngineCfg + LongHoldConfig.

ctx

Ctx and OperatorInfo — cross-cutting context threaded through the engine.

engine

Engine — the long-running stateful runtime plus the with_state helper (R1-R4 discipline).

errors

Engine error type.

state

EngineState — the single Mutex-guarded state object — plus the supporting types.