Slack agent flow (create_agent → provisioned Slack bot)

Composes the Slack extension skills into one conversational flow: a user tells an existing Slack-wired agent "create an agent called Research", and the new agent doesn't just exist as a send_message destination, it arrives in Slack as its own bot. The host provisions a Slack app for it (managed broker, or a workspace manager token), registers it as a slack-<name> instance, hot-starts the adapter in the running host, opens a DM between the new bot and the operator, opens a three-way MPIM (operator + originating bot + new bot) registered as an agent-to-agent room, and wires everything so both agents hear the room. The flow also adds two agent-facing room actions, create_room (one shared room with N agents at once, the team primitive) and add_to_room (grow a room by one agent), and extends the base create_agent tool with the flow's purpose / allow_guests / room parameters. Non-Slack sessions are untouched: create_agent from any other channel behaves exactly as upstream.

Canonical home. This directory on main is the skill's canonical source, the setup wizard and any direct apply read it from the checkout. The copy on the channels branch is a compatibility mirror for older checkouts whose setup fetches companions from there; edits land here, never there. The payload the Apply steps fetch with from-branch:channels stays on the channels branch, exactly like /add-slack's own.

Prerequisites

All prose below assumes these are already in place, in this order: