Simplified the shopper-facing message footer to just feedback

Under each assistant message on a shopper-facing surface, only the thumbs-up/down feedback controls remain. Copy, refresh, and the "more" menu (which held export-to-markdown) are gone from that surface.

This affects the two surfaces a shopper actually uses (the hosted public page and the embedded widget), plus the playground's User view, so what you preview there now matches what a shopper sees. Refresh was the biggest reason to change this: it re-runs the model for that turn, so leaving it exposed let a shopper regenerate an answer for free, on your bill. Copy and export are built for reviewing a transcript, not for a shopping conversation, so they're gone too.

Nothing changes in the playground's Technical view or in a conversation's read-only transcript under Conversations: both keep the full footer (copy, refresh, feedback, export), since that's where you review what the agent actually did.