package:dart_mcp v0.4.1

• Expose various private methods on MCP server mixins as public methods, with
  @mustCallSuper annotations. This allows intercepting calls for logging,
  metrics, or other purposes.
• Fix the resource parameter type on EmbeddedResource to be
  ResourceContents instead of Contents.
  • Note: This is technically breaking but the previous API would not have
    been possible to use in a functional manner, so it is assumed that it had
    no usage previously.
• Fix the type getter on EmbeddedResource to read the actual type field.
• Add toJson method to the CreateMessageResult of a sampling request.