theater setup manifest.toml — load the actor and set up its task loops,
but do NOT call actor.init. Used by replay (the replay handler walks
the recorded chain and fires init from there) and by callers that want
to drive init themselves with custom typed params.
theater spawn manifest.toml — load the actor, set up its task loops,
AND call its theater:simple/actor.init export before returning control
to the caller. The runtime auto-inits (PR A in ticket #27); the CLI
doesn’t fire init itself.