Task: Add Elicitation Support

[ezynda3]

Priority: Medium
Breaking Change: No

Description: Servers can now request additional information from users during interactions via elicitation requests.

Implementation Tasks:

• Add ElicitRequest and ElicitResult types
• Implement elicitation capability in server
• Add client-side elicitation handling
• Support for structured elicitation with request schemas
• Add elicitation examples (user confirmation, form filling)
• Implement proper error handling for cancelled elicitations

Files to Update:

• mcp/types.go
• server/server.go
• client/ (all transport implementations)

Notes: Requires bidirectional transport (SSE, WebSocket, or stdio). Not available for simple HTTP request/response.