docs: update research to casual tone and add AI caveat

- Changed formal academic language to more casual/humble tone
- Added important caveat about AI-executed research to all documents
- Made section headings more conversational
- Clarified this is an experiment in AI-assisted research, not equivalent to human research

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

Co-Authored-By: Claude <[email protected]>

Author: danielmiessler