Fix: Restrict Namer model dropdown to text-generation capable models

[raftaar1191]

Summary

Fixes #1219.

The model selection dropdown on the Plugin Check Namer tool displayed all available AI models, including those that don't support text-to-text generation (e.g. embedding models, vision-only models, audio models like gpt-4o-audio-preview). This caused confusion and would result in errors when a non-text-generation model was selected and used.

Changes

• includes/Traits/AI_Utils.php: Added model_supports_text_generation() helper method to the AI_Utils trait that inspects ModelMetadata::getSupportedCapabilities() from the WP 7.0 AI Client and checks for the text_generation capability value.
• Modified get_filtered_ai_models() to skip models that do not pass the capability check, so only text-generation capable models are returned for the dropdown.
• The helper gracefully falls back to true (include the model) when getSupportedCapabilities() is not available, ensuring backward compatibility.

How to Test

1. Ensure you have WordPress 7.0+ with at least one AI connector configured (including a provider that exposes multiple model types, e.g. OpenAI which has both gpt-4o and text-embedding-3-small).
2. Go to WP Admin → Tools → Plugin Check Namer.
3. Open the model dropdown.
4. Verify that only text-generation models are listed — embedding models, audio-only models, and image-generation models should not appear.

Closes #1219

[github-actions]

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Co-authored-by: raftaar1191 <raftaar1191@git.wordpress.org>
Co-authored-by: davidperezgar <davidperez@git.wordpress.org>

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[Copilot]

Pull request overview

Filters the Plugin Check Namer’s AI model dropdown to only show models that can perform text generation, reducing user confusion and preventing incompatible selections.

Changes:

• Added a model_supports_text_generation() helper to detect the text_generation capability from model metadata.
• Updated get_filtered_ai_models() to exclude models that don’t support text generation.

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[davidperezgar]

Hello! Thanks for the PR. Please fix linting errors.