/simplify-code review found _poll_for_token has a second caller:
web_server._nous_poller (dashboard/desktop device login), which surfaces
str(e) as the UI error_message — so wrapping only in
_nous_device_code_login left the dashboard showing the bare timeout.
Move the enrichment into _poll_for_token's deadline raise so every
caller inherits the guidance, and drop the now-redundant try/except
wrap in the CLI login. Add a source-level regression test driving the
real poll loop (authorization_pending stub client) to the deadline.