Auto-Run support for Group Chats

[sshpuntoff]

Add Auto-Run capability to group chats. The moderator owns the document and drives execution:

1. Moderator reads the Auto-Run doc
2. Picks next unchecked task
3. Delegates to participants via normal group chat routing
4. Waits for completion/synthesis
5. Marks checkbox
6. Repeats until done

Chat notifications should be suppressed during Auto-Run execution to avoid flooding — the conversation transcript itself serves as the execution log.

This keeps the existing group chat routing intact and avoids bridging the batch processor with group chat state. The moderator is the batch processor.

[kianhub]

This should become possible soon, as we introduce auto-run execution for agents.
I think this is a really nice approach for extremely long-running and probably cross-repo issues.