Add setter-based handlers for MCP request/notification forwarding

- Add oncalltool, onlistresources, onlistresourcetemplates, onreadresource, onlistprompts setters for Guest UI → Host requests
- Add sendToolListChanged, sendResourceListChanged, sendPromptListChanged methods for Host → Guest UI notifications
- Refactor connect() to use new setters with inlined callbacks
- Update documentation to clarify optional client parameter behavior
- Remove unused forwardRequest/forwardNotification helper methods

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

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

Author: ochafik