docs: redesign README with AI Agent focus and improved engagement

- Lead with the AI Agent as the main feature
- Add engaging demo conversation showing agent capabilities
- Streamlined quick start section
- Added keyboard shortcuts and chat commands reference
- Added Syncable Platform CTA at top and bottom
- Collapsible technology list for cleaner presentation
- Professional yet approachable tone

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

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

Author: 2 people