- Add helpers.py with connection management utilities:
- with_connection: context manager for connection lifecycle
- submit_command: execute command and return CommandFuture
- execute: run command with auto connection, raise on failure
- try_execute: run command with auto connection, return result
- Add CommandExecutionError to exec.py for typed error handling
with access to exit_code, stderr, and full result
- Remove run_command method from VirtualEnvironment base class
(now available as submit_command helper)
- Update all call sites to use new helper functions:
- sandbox/session.py
- sandbox/storage/archive_storage.py
- sandbox/bash/bash_tool.py
- workflow/nodes/command/node.py
- Add comprehensive unit tests for helpers with connection reuse
