Remove exit_code and status_message from the Actor constructor #1186

The Actor constructor accepts exit_code and status_message (_actor.py#L125-L154). Both describe how the run ends, which isn't known when the Actor is created. They also don't reliably reach the end of the run: Actor.exit() assigns its own defaults, so a bare await Actor.exit() resets them to 0 and None (#L511-L533). Only the async with Actor(...) path keeps them. The JS SDK takes these values only in exit().

Keeping the constructor values through exit() would need a "not passed" marker for every exit() argument, since None is already meaningful for status_message and event_listeners_timeout. #1190 tried that and was closed: it puts a private type into the public signatures for values that shouldn't be set in the constructor.

Remove both parameters from the constructor in v5. This is a breaking change: callers pass them to Actor.exit() / Actor.fail() instead, or set Actor.exit_code / Actor.status_message when using the context manager.

Acceptance criteria

• Actor(...) no longer accepts exit_code or status_message.
• The v5 upgrading guide lists the removal and the replacements.

✍️ Drafted by Claude Code