A coordinator role for a session

[YoanWai]

A coordinator is one session whose job is to run the others. Tasks and messages already let sessions share work. What is still open is how a session takes that role when it starts, and what people need from it.

@ydewit ran into this while adding named instruction presets in #745. A preset was a way to launch a session that already knew the job. He also asked whether that job should be the named agent some tools already have. Saved prompts stay the reusable text you can paste when a session starts, or later. This thread is the coordinator role.

These already sit next to it.

• RFC: Group Coordination #757 who a session may message, kill, or spawn
• Show who messaged whom and a short subject, instead of the full message body, to the person watching #761 what you see when one session messages another
• Allow disabling the session-pair message cap for coordinator workflows #776 the cap on messages between a pair, which gets in the way of a coordinator
• Let an external coordinator read file reservations, and optionally turn the reservation tools off #774 letting an outside coordinator read file reservations
• Command Code and Hermes sessions get no coordination guidance #707 coordination guidance for Command Code and Hermes
• [Spike] Named agent definitions spawnable on any CLI #500 whether one named role can spawn on every tool

If you run a coordinator today, what do you need that session to do? How do you want to start it? If your tool already has a named agent, should the session start as that agent?