feat(mcp): add docs query helper script

[pcharbon70]

Summary

• add a small Elixir helper that asks the running docs MCP HTTP endpoint questions from this repo
• add a minimal MCP HTTP client plus CLI modes for search, direct doc fetch, and section listing
• document the helper in the README and cover it with focused MCP CLI tests

Testing

• mix compile --warnings-as-errors
• mix credo --strict
• mix test test/agent_jido/mcp
• mix run scripts/ask_mcp_docs.exs -- "How do plugins work?"