Poll and command shared Alamo thermostats

Poll and command shared Alamo thermostats

One gateway worker shares status polls and the request budget across its
thermostats. Three missed observations publish offline, and successful
feedback restores online. Commands read a fresh baseline, verify power
off before target changes, and verify the target before power on.

The shared ledger records each outcome before feedback or result sends,
so duplicate commands replay stable results without another exchange.
Caller cancellation preserves independent failures, and HTTP errors omit
sensitive request and response data. The command keeps its empty driver
list so construction cannot start a device connection.

Issue: 5947f38