Contract validation

If a handler is missing required methods or schema definitions, the gem raises an ArgumentError on first request with a full diagnostic:

If a handler is missing required methods or schema definitions, the gem raises an ArgumentError on first request with a full diagnostic:

MyHandler does not satisfy the McpAuthorization handler contract.

Problems:
  - missing instance method #call
  - missing instance method #description
  - missing output schema (define # @rbs type output = variant1 | variant2 | ...)

A handler class should look like:

  class MyHandler
    include McpAuthorization::DSL

    # @rbs type output = success | error

    def description
      "What this tool does"
    end

    #: (name: String, ?force: bool @requires(:admin)) -> Hash[Symbol, untyped]
    def call(name:, force: false)
      # ...
    end
  end

Collected from README.md in the repository. Edit it there, not here.