Add LSP comparison FAQ to README (#9)

## Summary
- Adds a new FAQ entry explaining how Code Navigator differs from
Language Server Protocol (LSP)
- Covers three key differentiators: pre-computed vs on-demand, AI token
optimization, and portability

## Test plan
- [x] Verify FAQ renders correctly in markdown preview
- [x] Check formatting matches existing FAQ items

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

Co-authored-by: VibeXP Bot <bot@vibexp.io>
Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>

Author: 3 people

README.md

@@ -607,6 +607,15 @@ See [CONTRIBUTING.md](CONTRIBUTING.md) for detailed instructions. Contributions
 
 </details>
 
+<details>
+<summary><b>How is this different from using a language server (LSP)?</b></summary>
+
+- **Pre-computed vs On-demand**: Index once, query instantly — no server running per request
+- **AI-optimized**: Minimal token output for relationships, not IDE features like completions/hover
+- **Portable**: Single `.bin` file — no server connection or session state needed
+
+</details>
+
 ## 🤝 Contributing
 
 We welcome contributions! See [CONTRIBUTING.md](CONTRIBUTING.md) for: