Add the WP Performance Action for GitHub unit tests

[marcusquinn]

• https://github.com/swissspidy/wp-performance-action

[superdav42]

Dispatching worker.

• Model: sonnet (anthropic/claude-sonnet-4-6, default round-robin)
• Branch: new branch from main
• Scope: Add WP Performance Action to GitHub CI unit test workflow
• Attempt: 1 of 1