Each AI response has a copy-to-clipboard button

Users copy AI responses constantly — to paste code into an editor, share an answer in a work chat, or archive an explanation. Forcing manual text selection is a per-message papercut that accumulates across the lifetime of the product, and on mobile it is actively painful: text selection on long messages frequently selects the wrong range or triggers system menus. A per-message copy button is table-stakes for any chat interface that expects repeat use.

In src/components/chat/MessageBubble.tsx, add a copy button wired to navigator.clipboard.writeText() with a brief checkmark-confirmation state, and reveal it on hover via Tailwind's group/group-hover utilities to keep the resting UI clean.

const [copied, setCopied] = useState(false);
const handleCopy = () => {
  navigator.clipboard.writeText(message.content);
  setCopied(true);
  setTimeout(() => setCopied(false), 2000);
};