The single next move for this caller, with the command that executes it.

Returns EXACTLY ONE item — the top of the existing attention ranking; no new scoring model exists here. actor says who owns the move: for an agent item, command is taken from the action's timing.available_commands and is executable as-is once body_template is filled; for a human item, for_human says what to look at and why, and an agent executing it would be recording work it did not do. handoff is what a successor agent needs to continue without reading the history. When nothing is pending, rank is null and message explains that in one sentence.