chore: Organize documentation into docs/ folder

Moved all documentation files into organized structure:
- Root .md files → docs/
- binaries/README.md → docs/binaries-setup.md
- tests/manual/*.md → docs/testing/

New structure:
├── README.md (stays at root - GitHub standard)
├── docs/
│   ├── CLAUDE.md
│   ├── TODO.md
│   ├── HANDOFF_NOTES.md
│   ├── UNIVERSAL_HANDOFF.md
│   ├── FEATURES.md
│   ├── SECURITY_REVIEW.md
│   ├── GITHUB_PROJECTS_SYNC.md
│   ├── OPEN_TODOS.md
│   ├── binaries-setup.md
│   └── testing/
│       ├── README.md
│       ├── TESTING_GUIDE.md
│       ├── TEST_REPORT_TEMPLATE.md
│       └── TEST_URLS.md

Result: Clean root directory with organized documentation.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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