fix(server/a2a): structured error parity with MCP — emit field/details/retry_after, catch decisioning AdcpError#542

bokelley wants to merge 2 commits intomainadcontextprotocol/adcp-client-python:mainfrom

claude/issue-530-a2a-structured-error-parityadcontextprotocol/adcp-client-python:claude/issue-530-a2a-structured-error-parityCopy head branch name to clipboard