Run a shell command in the managed runtime.

- Pass only `command` for normal synchronous execution and wait for the command to finish.
- Set `background=true` only when the task should continue after the current tool call returns.
- Use `workdir` only when the command must run somewhere other than the default execution root; it may be absolute or relative, but it must still resolve inside the workspace writable roots.
- Use `tty=true` only for commands that require an interactive terminal.
- Prefer this tool over older exec-session tools.
