Add TARGET_FIELDS to config validation

[arturpragacz]

Proposed change

New streamlined TARGET_FIELDS was added for use in LLM fields serializer.

TARGET_SERVICE_FIELDS, that was used before, includes a lot of bloat, that accumulated over the years. That schema accepts things like:

• non-string entity ids
• upper- and mixed-case entity ids
• entity entry ids in addition to entity ids
• templates
• literal strings "all" or "none" and their variants differing in case

None of that should be present in the validation schema for the LLMs, as we want them to always give us the right output, and don't need to be involved with all that accumulated baggage.

The new schema should also be used for the new targeted conditions and triggers, as we don't have to concern ourselves with backwards compatibility there, and should be stricter in the input we accept.

Type of change

• Dependency upgrade
• Bugfix (non-breaking change which fixes an issue)
• New integration (thank you!)
• New feature (which adds functionality to an existing integration)
• Deprecation (breaking change to happen in the future)
• Breaking change (fix/feature causing existing functionality to break)
• Code quality improvements to existing code or addition of tests

Additional information

• This PR fixes or closes issue: fixes #
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• Link to frontend pull request:

Checklist

• The code change is tested and works locally.
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• Tests have been added to verify that the new code works.

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[Copilot]

Pull Request Overview

This PR introduces a new TARGET_FIELDS constant for use in LLM field serialization, replacing the previous use of TARGET_SERVICE_FIELDS. The change streamlines target field validation by simplifying the schema structure to only accept arrays of strings for each target type (entity_id, device_id, area_id, floor_id, label_id).

Key changes:

• Adds a new TARGET_FIELDS validation schema with simplified array-only structure
• Updates the LLM selector serializer to use the new TARGET_FIELDS instead of TARGET_SERVICE_FIELDS
• Updates corresponding tests to reflect the simplified schema structure

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
homeassistant/helpers/config_validation.py	Adds new TARGET_FIELDS constant with simplified array-based validation for target fields
homeassistant/helpers/llm.py	Updates selector serializer to use new TARGET_FIELDS instead of TARGET_SERVICE_FIELDS
tests/helpers/test_llm.py	Updates test expectations to match the simplified target selector schema output

[MartinHjelmare]

Please explain in the PR description why it's good to use the new validator instead of TARGET_SERVICE_FIELDS, in the llm helper.

[arturpragacz]

@MartinHjelmare Done.

[abmantis]

Thanks @arturpragacz !