Adds a new standalone /deepdive page with its own platform.css/platform.js,
wires it into the dot-nav as an external entry, and updates the dot-nav
docblock to reflect the new seven-entry layout. Also drops in BUSINESS.md
and reference material under architecture boxes/ and examples/.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
