feat: merge Surge 1.0.x into drupal/ai_best_practices

Import Composer plugin, skills/agents CLI, tests, and phpunit config from Surge 1.0.x; rebrand public surface to Drupal\AiBestPractices, composer script drupal-ai, and project config ai_best_practices.yaml.

Intentional differences from upstream Surge:

• No Composer require on drupal/ai_skills;
• Removing the template sections for AGENTS.md creation, we will use our own AGENTS.md with markers that allow us to (re-)generate it.

This is purely based as feedback/start point So we can easily create value when installing drupal/ai_best_practice whilst collecting feedback and updating/removing/extending parts that Surge already offered.

Closes #3584903