op: action effects can make a clock action pause #268

Area

Engine: clock actions (clock: turn-boundary) and content's op: action effects (#238).

Version

Current main.

Input

Content with an op: action effect at a tagged step of a clock action, where the run hands off or runs an action that can pause (a choice or dice the app must supply).

Expected

A clock action runs with nothing the app supplies (#208); load rejects anything that can make it pause, as it does for the clock action's own steps (invalid-clock-action).

Actual

Load checks only the clock action's own steps, not op: action effects reaching them, so the clock action can pause. Found while fixing the spec docs (#265). Proposed fix: report such effects as invalid-clock-action at load.