Add StepType CLI commands for step type discovery

[saraichinwag]

Summary

Add WP-CLI commands for step type discovery and validation. StepTypeAbilities exist but have no CLI wrapper.

Running Version

v0.39.0

Abilities to Wrap

• datamachine/get-step-types - List all step types or get one by slug
• datamachine/validate-step-type - Validate a step type slug

Proposed Commands

wp datamachine step-types list
wp datamachine step-types get <slug>
wp datamachine step-types validate <slug>

Priority

🟢 Low - Developer tooling, niche use case