- web host boots CommandService + command-goal; session.prompt intercepts
a lone text block starting with '/' and executes it as a command
(unknown -> RPC unknown-command, usage error -> RPC command-error, so
the composer restores the draft and shows the error strip) instead of
sending it to the model — symmetric with the ACP adapter
- prompt response carries command result text on the wire for future UI
- api-proxy also lands the host-side goals RPC handlers
_Kerman