docs: reorganize directory structure for clarity

Simplified root directory from 24 to 14 visible items.

Changes:
- Created docs/ subdirectories:
  - docs/api/ - Technical documentation
  - docs/governance/ - Community and contribution docs
  - docs/standards/ - Compliance documentation
  - docs/changelog/ - Version history

- Created .build/ directory:
  - Moved Justfile, Containerfile, Mustfile
  - Moved config/ subdirectory
  - Hidden to avoid confusion with build artifacts

- Moved CLAUDE.md to .claude/PROJECT.md

- Created navigation guides:
  - NAVIGATION.adoc - Repository structure guide
  - docs/README.adoc - Documentation directory guide

- Updated all links in README.adoc to reflect new paths

Root directory now contains only:
- Essential files: README, LICENSE, VERSION, package.json
- Core directories: src/, tests/, examples/, scripts/, docs/
- Metadata: STATE.scm, META.scm, ECOSYSTEM.scm
- Navigation: NAVIGATION.adoc
- Hidden: .build/, .claude/, .github/, .machine_readable/

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

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