Add a new chat channel's layer-1 setup guide — the in-dashboard <Channel>SetupGuide that walks a developer through connecting the channel itself (create app/bot → save credentials → install/verify → send first message) with live connection detection — in apps/dashboard, following the existing Slack, MS Teams, and Telegram guides. Use when a new agent channel needs its numbered setup stepper, credential drawer wiring, and connectedAt polling under components/agents.