Fix main device type and name updates

[wilbersl]

Problem

When device.name = "main" is set in devices.toml, the plugin attempts to update the name and type of the main device. This results in an error:

[te/device/main//] {"@type": "child-device", "name": "main", "type": "modbus-device", "time": "2026-03-19T08:53:51.876779+00:00"}
[te/errors] Updating the entity type of device/main// is not supported
[te/device/main///twin/name] "main"
[te/device/main///twin/time] "2026-03-19T08:53:51.876779+00:00"
[te/device/main///twin/type] "modbus-device"

Expected Behavior

No changes should be applied to the device name or type when referring to the main device.

Solution

Skip creating a child device when the device name is main.