fix: finalize learning-path structure, breadcrumbs, and links

[BotshareAI]

Final structural alignment

Re-audits the live framework against the approved detailed Layer-2 architecture and corrects the centre of the site.

Learning-path navigation

Promotes the approved technical sequence to the top level:

Foundations → Build → Use → Configure → Customize → Maintain and repair → Reference

This replaces the additional wrapper introduced earlier and preserves the exact detailed substructure for robot anatomy, navigation, manipulation, Embodied AI, ROS 2, safety, assembly 00–10, electronics, bring-up, calibration, operation, configuration, customization, service, and the 12-repository × 7-section reference mirror.

Solutions, Build a Business, Academy, Community, and About remain as additive ecosystem layers. The real Documentation Standard and Academy portfolio are explicitly included in navigation.

External links

• All HTTP(S) links leaving docs.openamrobot.ai open in a new tab
• Adds rel="noopener noreferrer"
• Internal links, anchors, email, and phone links remain in the current tab
• Works after MkDocs Material instant-navigation page changes
• Adds a subtle external-link indicator where appropriate

Breadcrumbs

• Restores persistent hierarchy breadcrumbs for nested pages
• Generates Home / section / subsection / current page
• Intermediate levels are navigable
• Current page has aria-current="page"
• Re-renders correctly after instant navigation

Reader tracks

Adds visible inferred track chips to every relevant section: Beginner, Builder, Operator, Integrator, Developer, Entrepreneur, Learner, and Partner.

Verification

• All proposed technical page paths are implemented; start-here/index.md intentionally replaces start-here.md to produce the same /start-here/ route without a MkDocs output collision
• node --check docs/javascripts/site-enhancements.js passes
• python -m mkdocs build --strict passes locally with social temporarily disabled; production keeps it enabled
• All normal pages are in navigation; only 404.md is intentionally excluded
• git diff --check passes