Alter Template Helper editor to avoid user confusion.

[Didgeridrew]

Since its introduction, there have been regular posts on the forums and Discord from users who are confused that their helpers are always "unavailable" or by error messages they receive in the template renderer within the editor. The vast majority of the time this is due to the user not understanding that the "State template" field is for templates only, not YAML configuration.

Example 1
Example 2
Example 3

The UI of the editor needs to make it more obvious/explicit that the "State template" field is only for Jinja templating and that "advanced" options like triggers, actions, attributes, and availability are not supported.

If there is no current plan to expand the Template Helper to allow the "advanced" options, we also need to address the Template Docs: UI Configuration to also make these limitations explicit and include an example screenshot.

[karwosts]

Perhaps something like this? I'm thinking maybe it's sufficient to just look for the string template:, sensor: , or state: in the user input, or is that ever a valid syntax that would be a false positive? (though it is just a warning so that wouldn't obstruct anything)

If you think the docs are missing something, feel free to PR some additional language there that you think would be helpful.

[Didgeridrew]

I think that's good, as long as it also catches binary_sensor:, platform:, and value_template:... since ChatGPT seems to prefer the Legacy style template sensors config, so we're seeing a lot of the last two.

[Didgeridrew]

It looks like the warning may be needed for template fields elsewhere...

https://community.home-assistant.io/t/send-phone-notification-based-on-email-subject/742638

[karwosts]

Completed @ #21545