Implement the Copilot SDK user input round-trip in the backend:
- add user-input-requested and resolve-user-input protocol DTOs
- add a CopilotUserInputCoordinator that mirrors approval flow with
pending TaskCompletionSource state and explicit resolution
- wire SessionConfig.OnUserInputRequest through CopilotAgentBundle
and CopilotWorkflowRunner
- extend SidecarProtocolHost to emit user input events, accept
resolve-user-input commands, and filter ask_user from runtime
approval tools
- add regression tests for the new coordinator and protocol flow
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>