Add documentation for sensor entities to Airobot integration (#42140)

Author: mettolen

source/_integrations/airobot.markdown

@@ -65,7 +65,7 @@ This is useful when:
 
 ## Supported functionality
 
-The **Airobot** integration provides climate control functionality with comprehensive temperature management and preset modes.
+The **Airobot** integration provides climate control functionality with comprehensive temperature management and preset modes, as well as detailed sensor monitoring.
 
 ### Climate
 
@@ -85,10 +85,41 @@ The thermostat is represented as a climate entity with the following capabilitie
   - **Away**: Use the AWAY temperature setpoint (typically lower for energy savings)
   - **Boost**: Temporarily boost heating for 1 hour, then return to the previous mode
 
+### Sensors
+
+The integration provides the following sensor entities to monitor your thermostat and environment:
+
+#### Environmental sensors
+
+- **Air temperature**: The measured air temperature in the room (in °C).
+- **Floor temperature**: The measured floor temperature (in °C). Only available if a floor temperature sensor is connected to the thermostat.
+- **Humidity**: The measured relative humidity in the room (in %).
+- **Carbon dioxide**: The measured carbon dioxide concentration in the room (in ppm). Only available if the thermostat has the optional carbon dioxide sensor.
+- **Air quality index**: The calculated air quality index based on carbon dioxide levels. Only available if the thermostat has the optional carbon dioxide sensor.
+
+#### Diagnostic sensors
+
+The following diagnostic sensors are disabled by default. You can enable them in the entity settings if needed:
+
+- **Device uptime**: The time (in hours) since the thermostat was last restarted.
+- **Heating uptime**: The cumulative time (in hours) the heating has been active since the thermostat was last restarted.
+
+#### System sensors
+
+- **Errors**: The current error count on the thermostat. A value of 0 indicates normal operation.
+
 ## Data updates
 
 The **Airobot** integration {% term polling polls %} data from the thermostat every 30 seconds. This interval matches the thermostat's internal measurement cycle, ensuring efficient data synchronization without overwhelming the device.
 
+## Known limitations
+
+- **Local API only**: The integration only supports the local REST API. Cloud-based control through the Airobot cloud service is not supported.
+- **Manual API enablement**: The local REST API must be manually enabled on the thermostat before the integration can connect. It is disabled by default for security reasons.
+- **Firmware requirements**: Only firmware version 1.8 or later is supported. Older firmware versions do not provide the local REST API.
+- **Heating only**: The thermostat is designed for floor heating control only and does not support cooling modes.
+- **Optional sensors**: carbon dioxide and floor temperature sensors are only available if the corresponding hardware is installed in your thermostat model.
+
 ## Troubleshooting
 
 ### Cannot connect to thermostat