fix(shared): preserve MCPError payload on pickle#2478

MukundaKatta wants to merge 2 commits intomodelcontextprotocol:mainmodelcontextprotocol/python-sdk:mainfrom

MukundaKatta:codex/mcp-error-pickle-safeMukundaKatta/python-sdk:codex/mcp-error-pickle-safeCopy head branch name to clipboard