CLI support for image alt text generation

[alaminfirdows]

Summary

Implement WP-CLI command to generate alternative text for image attachments using the WordPress AI Client, following WordPress/ai#44.

What was added

New subcommand under wp ai generate:

wp ai generate alt-text <attachment_id>

Capabilities

• Validates attachment exists and is image type
• Converts image to data URI for vision model processing
• Generates alt text via WordPress AI Client
• Enforces 125-character limit (WCAG guideline)
• Updates _wp_attachment_image_alt post meta
• Supports all standard options: --provider, --model, --temperature, --top-p, --top-k, --max-tokens, --system-instruction

Example usage

$ wp ai generate alt-text 123
Success: Alt text generated and saved for attachment 123: A WordPress logo on a blue background

Implementation

• Added generate_alt_text() private method to AI_Command class
• Uses WordPress AI Client with_file() builder method for vision input
• Error handling: missing attachment, non-image type, unreadable file, unsupported model
• Test coverage: added Behat scenarios for error cases

Related

• Upstream: Alt Text Generation WordPress/ai#44
• Branch: feat/alt-text-generation

[swissspidy]

I'm not sure this warrants its own command. Alt text generation is simply generating text while providing an input image.

Could we perhaps just support this in wp ai generate text and allow providing input image(s)? They could be local, URLs, or attachment IDs.