reorganize reference docs for better navigation #1739
Description
Consider reorganizing reference docs for better navigation
Follow-up to #1726
What's incorrect or missing?
- Advanced references appear throughout Fundamentals and Capabilities
- Hard for users to differentiate between intro-level docs and deep-dive material
What's the resolution?
- Separate advanced references (detailed config, architecture) into a distinct "Reference" or "Internals" section
- Keep onboarding and feature overviews in Fundamentals and Capabilities