Actual localhost MQTT experiment. No credentials or public broker.
Requires Python 3, paho-mqtt==2.1.0, and an actual Mosquitto 2.1.2 executable.
Create a virtual environment and install only the pinned client there.
Set MOSQUITTO_BIN to the exact executable, then:
  python test_mqtt_room.py
Tests use a temporary directory and a broker listener explicitly bound to 127.0.0.1
on a free high port. The broker is stopped and its files removed afterward.
Do not run these tests against a shared broker or add a LAN listener.
All values are synthetic. Host results are not Pi or ESP32 execution results.
