* Update StdioTransport documentation comments to indicate support for JSON-RPC batches
* Add server support for JSON-RPC batching
* Add client support for JSON-RPC batching
* Fix bug that caused error messages to be wrapped unnecessarily
* Rename Error to MCPError
* Conform MCPError to Swift.Error
* Use unqualified Error instead of Swift.Error
* Use unqualified MCPError instead of MCP.MCPError
* Rename file back to Error.swift
* Introduce top-level MCP namespace with nested Error typealias to provide deprecation notice for existing usage of MCP.Error
* Fix markup for MCP enum warning