Enhancement: Check status of non-closed PRs

If something isn't already merged, follow up to see if it's been merged since the last run.

Probably should submit this on the repo actor and then handle the follow-up command on both the user and repo levels

Start by tracing the existing PR status check and the repo actor, then follow how the follow-up command is handled at both user and repository levels. Done means non-closed PRs are checked again after the last run and their merged status is handled consistently in both paths.

Written by the indexing model from the issue text.