fix: consolidate reference routes and navigation cues

[BotshareAI]

Summary

• remove the redundant circled development-status icons from all navigation entries while retaining visible page-level development banners
• render breadcrumbs as one horizontal folder-style path
• consolidate Architecture, Repositories, Mobile Platform, Upper Body, Interfaces, and Communication under canonical /reference/ URLs
• redirect all legacy paths with mkdocs-redirects
• fold the obsolete Technical getting started router into Start here
• clarify the canonical-source policy: repositories own exact versions and contracts; this site teaches their meaning, selection, application, and verification
• correct obsolete /learn/... links and remaining links to legacy routes
• hide the redundant one-item left navigation sidebar on the homepage while retaining the top navigation and page table of contents

Why the icons disappeared

The circled i was generated by status: under-development metadata on every scaffold page. It was not a navigation control and did not add useful page-specific information. Development status remains clearly visible in each page banner.

Validation

• git diff --check
• zero remaining page-level status: metadata
• zero development-status icons in generated Build navigation
• legacy Architecture output redirects to /reference/architecture/
• generated homepage primary sidebar is marked hidden
• python -m mkdocs build --strict