Client Elicitation Support

[nickeddy]

Summary

Implements MCP client elicitation support as specified in the Model Context Protocol, allowing servers to request structured user input during interactions.

Features

• Multiple handler types: DefaultElicitationHandler, DeclineElicitationHandler, FunctionElicitationHandler,
  RateLimitedElicitationHandler
• Based on latest spec
• Tested with fastmcp server elicitation, mcp go-sdk
• Schema validation using jsonschema library

[nickeddy]

Realizing I should have looked at Issue #312 first. Apologies.

[hugowschneider]

Suggestion:
@nickeddy, it would be helpful to add a mechanism to determine the request_id beforehand or introduce an artificial identifier that can be set prior to the tool call (likely via Hooks). This identifier could then be used to map values during the elucidation handler call.
Use Case:
When a user interacts with an agent and the MCP server triggers an elicitation, I need to know—after the user responds—which callback to invoke from a dictionary structured as user_id -> callback. Having a pre-set identifier would allow me to reliably resolve the correct request.