Offline testing

Related guidance: getting-started/mock-setup.

Runnable examples: preflight.py.

Symbol	Summary
MockECN	Run a deterministic MQTT v5 test broker.
MockEvents	Expose synchronization events for deterministic asynchronous tests.
MockScenario	Store mutable deterministic fault controls for one mock instance.
FULL_ACCESS_TOKEN	Synthetic token with every mock-only ACL label for offline tests.