- Add system theme listener to detect OS theme changes in real-time
- Refactor to eliminate duplicate theme preference extraction
- Simplify getMermaidTheme function from switch statement to ternary
- Move render guard outside async function for better readability
- Update comments to be more concise and focused

The component now properly re-renders Mermaid diagrams when the OS theme changes while using "system" theme preference.

🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude <noreply@anthropic.com>