AI: Update php-ai-client to 1.3.0.

Updates the bundled `php-ai-client` library to version 1.3.0 and aligns the WordPress-specific prompt builder (`WP_AI_Client_Prompt_Builder`) with the upstream changes.

Key changes in php-ai-client 1.3.0:
* Adds video generation model interfaces.
* Enhances `PromptBuilder` with additional configuration methods.
* Improves `TokenUsage` and `ProviderMetadata` DTOs.
* Updates `MessagePart` DTO.

See release: https://github.com/WordPress/php-ai-client/releases/tag/1.3.0

Developed in https://github.com/WordPress/wordpress-develop/pull/11219

Props flixos90.
See #64591.




git-svn-id: https://develop.svn.wordpress.org/trunk@61942 602fd350-edb4-49c9-b593-d223f7449a82