Addresses Copilot review on #61348: the HTML-escaped role, while safe from
injection (quotes are escaped), still contains whitespace when a crafted role
is supplied, which splits the class attribute into several unintended CSS
classes. Keep the escaped role for the display badge, and reduce the raw role
to a single safe CSS token (alnum/-/_) for the class name. Real roles
(user/assistant/system/tool) are unchanged, so the existing .message-<role>
rules still match.
briandevans