Home Assistant Integration Improvements

[nanomad]

Summary

When remote commands to the vehicle fail (e.g. "Remote Instruction Failed", return code 4/8), there is currently no way for Home Assistant users to know about or react to the failure.

This feature should surface command errors via MQTT so they can be consumed in HA, either as an Event entity or a dedicated MQTT topic.

Sub-issues

• Feature request: Home Assistant Event entity for command errors #272
• FR: Report Error "Remote Instruction Failed," in an MQTT topic #102