Let users summon their custom Copilot mid-chat via:

/invoke [name] (e.g., /invoke CodeBot)

@mention (e.g., @LegalAI review this)

Why?

✓ No switching/importing chats

✓ Feels natural (like tagging a person)

✓ Great for teams (shared Copilots)

Bonus: Autocomplete for / or @ to show available Copilots.