Close the control service a handle refers to. For a local handle this is
at_control_stop(); for a remote handle it sends POST /v1/close, after
which that service stops accepting requests while its host process and any
app keep running. Neither path terminates a process. A close is not
revision-checked, so concurrent edits in an attached app never make it
fail; unsaved app edits stay in the app.
Usage
at_control_close(handle, call = rlang::caller_env())